Madhava series
Encyclopedia
In mathematics, a Madhava series is any one of the series in a collection of infinite series expressions all of which are believed to have been discovered by Sangamagrama Madhava (c. 1350 – c. 1425) the founder of the Kerala school of astronomy and mathematics. These expressions are the infinite power series expansions of the trigonometric sine
, cosine and arctangent functions
, and the special case of the power series expansion of the arctangent function yielding a formula for computing π. The power series expansions of sine and cosine functions are respectively called Madhava's sine series and Madhava's cosine series. The power series expansion of the arctangent function is sometimes called Madhava–Gregory series or Gregory–Madhava series. These power series are also collectively called Taylor–Madhava series. The formula for π is referred to as Madhava–Newton
series or Madhava–Leibnitz
series or Leibniz formula for pi or Leibnitz–Gregory–Madhava series. These further names for the various series are reflective of the names of the western
discoverers or popularizers of the respective series.
No surviving works of Madhava contain explicit statements regarding the expressions which are now referred to as Madhava series. However, in the writing of later members of the Kerala school of astronomy and mathematics like Nilakantha Somayaji
and Jyeshthadeva one can find unambiguous attributions of these series to Madhava. It is also in the works of these later astronomers and mathematicians one can trace the Indian proofs of these series expansions. These proofs provide enough indications about the approach Madhava had adopted to arrive at his series expansions.
and its commentaries can be safely assumed to be in "Madhava's own words". The translations of the relevant verses as given in the Yuktidipika commentary of Tantrasamgraha
(also known as Tantrasamgraha-vyakhya) by Sankara Variar
(circa. 1500 - 1560 CE) are reproduced below. These are then rendered in current mathematical notations.
. A translation of the verses follows.
Multiply the arc by the square of the arc, and take the result of repeating that (any number of times). Divide (each of the above numerators) by the squares of the successive even numbers increased by that number and multiplied by the square of the radius. Place the arc and the successive results so obtained one below the other, and subtract each from the one above. These together give the jiva, as collected together in the verse beginning with "vidvan" etc.
which is the infinite power series expansion of the sine function.
For such a reformulation, Madhava considers a circle one quarter of which measures 5400 minutes (say C minutes) and develops a scheme for the easy computations of the jiva′s of the various arcs of such a circle. Let R be the radius of a circle one quarter of which measures C.
Madhava had already computed the value of π using his series formula for π. Using this value of π, namely 3.1415926535922, the radius R is computed as follows:
Then
Madhava's expression for jiva corresponding to any arc s of a circle of radius R is equivalent to the following:
Madhava now computes the following values:
The jiva can now be computed using the following scheme:
This gives an approximation of jiva by its Taylor polynomial of the 11'th order. It involves one division, six multiplications and five subtractions only. Madhava prescribes this numerically efficient computational scheme in the following words (translation of verse 2.437 in Yukti-dipika):
vi-dvān, tu-nna-ba-la, ka-vī-śa-ni-ca-ya, sa-rvā-rtha-śī-la-sthi-ro, ni-rvi-ddhā-nga-na-rē-ndra-rung . Successively multiply these five numbers in order by the square of the arc divided by the quarter of the circumference (5400′), and subtract from the next number. (Continue this process with the result so obtained and the next number.) Multiply the final result by the cube of the arc divided by quarter of the circumference and subtract from the arc.
. A translation of the verses follows.
Multiply the square of the arc by the unit (i.e. the radius) and take the result of repeating that (any number of times). Divide (each of the above numerators) by the square of the successive even numbers decreased by that number and multiplied by the square of the radius. But the first term is (now)(the one which is) divided by twice the radius. Place the successive results so obtained one below the other and subtract each from the one above. These together give the śara as collected together in the verse beginning with stena, stri, etc.
which gives the infinte power series expansion of the cosine function.
As in the case of the sine series, Madhava considers a circle one quarter of which measures 5400 minutes (say C minutes) and develops a scheme for the easy computations of the śara′s of the various arcs of such a circle. Let R be the radius of a circle one quarter of which measures C. Then, as in the case of the sine series, Madhava gets
R = 3437′ 44′′ 48′′′.
Madhava's expression for śara corresponding to any arc s of a circle of radius R is equivalent to the following:
Madhava now computes the following values:
The śara can now be computed using the following scheme:
This gives an approximation of śara by its Taylor polynomial of the 12'th order. This also involves one division, six multiplications and five subtractions only. Madhava prescribes this numerically efficient computational scheme in the following words (translation of verse 2.438 in Yukti-dipika):
The six stena, strīpiśuna, sugandhinaganud, bhadrāngabhavyāsana, mīnāngonarasimha, unadhanakrtbhureva. Multiply by the square of the arc divided by the quarter of the circumference and subtract from the next number. (Continue with the result and the next number.) Final result will be utkrama-jya (R versed sign).
. A translation of the verses is given below.
Jyesthadeva has also given a description of this series in Yuktibhasa
.
Now, by just the same argument, the determination of the arc of a desired sine can be (made). That is as follows: The first result is the product of the desired sine and the radius divided by the cosine of the arc. When one has made the square of the sine the multiplier and the square of the cosine the divisor, now a group of results is to be determined from the (previous) results beginning from the first. When these are divided in order by the odd numbers 1, 3, and so forth, and when one has subtracted the sum of the even(-numbered) results from the sum of the odd (ones), that should be the arc. Here the smaller of the sine and cosine is required to be considered as the desired (sine). Otherwise, there would be no termination of results even if repeatedly (computed).
By means of the same argument, the circumference can be computed in another way too. That is as (follows): The first result should by the square root of the square of the diameter multiplied by twelve. From then on, the result should be divided by three (in) each successive (case). When these are divided in order by the odd numbers, beginning with 1, and when one has subtracted the (even) results from the sum of the odd, (that) should be the circumference.
Sine
In mathematics, the sine function is a function of an angle. In a right triangle, sine gives the ratio of the length of the side opposite to an angle to the length of the hypotenuse.Sine is usually listed first amongst the trigonometric functions....
, cosine and arctangent functions
Function (mathematics)
In mathematics, a function associates one quantity, the argument of the function, also known as the input, with another quantity, the value of the function, also known as the output. A function assigns exactly one output to each input. The argument and the value may be real numbers, but they can...
, and the special case of the power series expansion of the arctangent function yielding a formula for computing π. The power series expansions of sine and cosine functions are respectively called Madhava's sine series and Madhava's cosine series. The power series expansion of the arctangent function is sometimes called Madhava–Gregory series or Gregory–Madhava series. These power series are also collectively called Taylor–Madhava series. The formula for π is referred to as Madhava–Newton
Isaac Newton
Sir Isaac Newton PRS was an English physicist, mathematician, astronomer, natural philosopher, alchemist, and theologian, who has been "considered by many to be the greatest and most influential scientist who ever lived."...
series or Madhava–Leibnitz
Gottfried Leibniz
Gottfried Wilhelm Leibniz was a German philosopher and mathematician. He wrote in different languages, primarily in Latin , French and German ....
series or Leibniz formula for pi or Leibnitz–Gregory–Madhava series. These further names for the various series are reflective of the names of the western
Western world
The Western world, also known as the West and the Occident , is a term referring to the countries of Western Europe , the countries of the Americas, as well all countries of Northern and Central Europe, Australia and New Zealand...
discoverers or popularizers of the respective series.
No surviving works of Madhava contain explicit statements regarding the expressions which are now referred to as Madhava series. However, in the writing of later members of the Kerala school of astronomy and mathematics like Nilakantha Somayaji
Nilakantha Somayaji
Kelallur Nilakantha Somayaji was a major mathematician and astronomer of the Kerala school of astronomy and mathematics. One of his most influential works was the comprehensive astronomical treatise Tantrasamgraha completed in 1501...
and Jyeshthadeva one can find unambiguous attributions of these series to Madhava. It is also in the works of these later astronomers and mathematicians one can trace the Indian proofs of these series expansions. These proofs provide enough indications about the approach Madhava had adopted to arrive at his series expansions.
Madhava's series in modern notations
In the writings of the mathematicians and astronomers of the Kerala school, Madhava's series are described couched in the terminology and concepts fashionable at that time. When we translate these ideas into the notations and concepts of modern day mathematics, we obtain the current equivalents of Madhava's series. These present-day counterparts of the infinite series expressions discovered by Madhava are the following:| No. | Series | Name | Western discoverers of the seriesand approximate dates of discovery |
|---|---|---|---|
| 1 | sin x = x − x3 / 3! + x5 / 5! − x7 / 7! + ... | Madhava's sine series | Isaac Newton (1670) and Wilhelm Leibniz (1676) |
| 2 | cos x = 1 − x2 / 2! + x4 / 4! − x6 / 6! + ... | Madhava's cosine series | Isaac Newton (1670) and Wilhelm Leibniz (1676) |
| 3 | tan−1x = x − x3 / 3 + x5 / 5 − x7 / 7 + ... | Madhava's series for arctangent | James Gregory (1671) and Wilhelm Leibniz (1676) |
| 4 | π / 4 = 1 − 1 / 3 + 1 / 5 − 1 / 7 + ... | Madhava's formula for π | James Gregory (1671) and Wilhelm Leibniz (1676) |
Madhava series in "Madhava's own words"
None of Madhava's works containing any of the series expressions attributed to him has survived. These series expressions are found in the writings of the followers of Madhava in the Kerala school. At many places these authors have clearly stated that these are "as told by Madhava". Thus the enunciations of the various series found in TantrasamgrahaTantrasamgraha
Tantrasamgraha is an important astronomical treatise written by Nilakantha Somayaji, an astronomer/mathematician belonging to the Kerala school of astronomy and mathematics....
and its commentaries can be safely assumed to be in "Madhava's own words". The translations of the relevant verses as given in the Yuktidipika commentary of Tantrasamgraha
Tantrasamgraha
Tantrasamgraha is an important astronomical treatise written by Nilakantha Somayaji, an astronomer/mathematician belonging to the Kerala school of astronomy and mathematics....
(also known as Tantrasamgraha-vyakhya) by Sankara Variar
Sankara Variar
Sankara Variar was an astronomer-mathematician of the Kerala school of astronomy and mathematics who lived during the sixteenth century CE...
(circa. 1500 - 1560 CE) are reproduced below. These are then rendered in current mathematical notations.
In Madhava's own words
Madhava's sine series is stated in verses 2.440 and 2.441 in Yukti-dipika commentary (Tantrasamgraha-vyakhya) by Sankara VariarSankara Variar
Sankara Variar was an astronomer-mathematician of the Kerala school of astronomy and mathematics who lived during the sixteenth century CE...
. A translation of the verses follows.
Multiply the arc by the square of the arc, and take the result of repeating that (any number of times). Divide (each of the above numerators) by the squares of the successive even numbers increased by that number and multiplied by the square of the radius. Place the arc and the successive results so obtained one below the other, and subtract each from the one above. These together give the jiva, as collected together in the verse beginning with "vidvan" etc.
Rendering in modern notations
Let r denote the radius of the circle and s the arc-length.- The following numerators are formed first:
-
-
- These are then divided by quantities specified in the verse.
-
- Place the arc and the successive results so obtained one below the other, and subtract each from the one above to get jiva:
-
-
Transformation to current notation
Let θ be the angle subtended by the arc s at the centre of the circle. Then s = rθ and jiva = r sin θ. Substituting these in the last expression and simplifying we get
which is the infinite power series expansion of the sine function.
Madhava's reformulation for numerical computation
The last line in the verse ′as collected together in the verse beginning with "vidvan" etc.′ is a reference to a reformulation of the series introduced by Madhava himself to make it convenient for easy computations for specified values of the arc and the radius.For such a reformulation, Madhava considers a circle one quarter of which measures 5400 minutes (say C minutes) and develops a scheme for the easy computations of the jiva′s of the various arcs of such a circle. Let R be the radius of a circle one quarter of which measures C.
Madhava had already computed the value of π using his series formula for π. Using this value of π, namely 3.1415926535922, the radius R is computed as follows:
Then
- R = 2 × 5400 / π = 3437.74677078493925 = 3437 arcminutes 44 arcseconds 48 sixtieths of an arcsecond = 3437′ 44′′ 48′′′
Madhava's expression for jiva corresponding to any arc s of a circle of radius R is equivalent to the following:
Madhava now computes the following values:
| No. | Expression | Value | Value in Katapayadi system Katapayadi system Kaṭapayādi system of numerical notation is an ancient Indian system to depict letters to numerals for easy remembrance of numbers as words or verses... |
|---|---|---|---|
| 1 | R × (π / 2)3 / 3! | 2220′ 39′′ 40′′′ | ni-rvi-ddhā-nga-na-rē-ndra-rung |
| 2 | R × (π / 2)5 / 5! | 273′ 57′′ 47′′′ | sa-rvā-rtha-śī-la-sthi-ro |
| 3 | R × (π / 2)7 / 7! | 16′ 05′′ 41′′′ | ka-vī-śa-ni-ca-ya |
| 4 | R × (π / 2)9 / 9! | 33′′ 06′′′ | tu-nna-ba-la |
| 5 | R × (π / 2)11 / 11! | 44′′′ | vi-dvān |
The jiva can now be computed using the following scheme:
- jiva = s − (s / C)3 [ (2220′ 39′′ 40′′′) − (s / C)2 [ (273′ 57′′ 47′′′) − (s / C)2 [ (16′ 05′′ 41′′′) − (s / C)2[ (33′′ 06′′′) − (s / C)2 (44′′′ ) ] ] ] ]
This gives an approximation of jiva by its Taylor polynomial of the 11'th order. It involves one division, six multiplications and five subtractions only. Madhava prescribes this numerically efficient computational scheme in the following words (translation of verse 2.437 in Yukti-dipika):
vi-dvān, tu-nna-ba-la, ka-vī-śa-ni-ca-ya, sa-rvā-rtha-śī-la-sthi-ro, ni-rvi-ddhā-nga-na-rē-ndra-rung . Successively multiply these five numbers in order by the square of the arc divided by the quarter of the circumference (5400′), and subtract from the next number. (Continue this process with the result so obtained and the next number.) Multiply the final result by the cube of the arc divided by quarter of the circumference and subtract from the arc.
In Madhava's own words
Madhava's cosine series is stated in verses 2.442 and 2.443 in Yukti-dipika commentary (Tantrasamgraha-vyakhya) by Sankara VariarSankara Variar
Sankara Variar was an astronomer-mathematician of the Kerala school of astronomy and mathematics who lived during the sixteenth century CE...
. A translation of the verses follows.
Multiply the square of the arc by the unit (i.e. the radius) and take the result of repeating that (any number of times). Divide (each of the above numerators) by the square of the successive even numbers decreased by that number and multiplied by the square of the radius. But the first term is (now)(the one which is) divided by twice the radius. Place the successive results so obtained one below the other and subtract each from the one above. These together give the śara as collected together in the verse beginning with stena, stri, etc.
Rendering in modern notations
Let r denote the radius of the circle and s the arc-length.- The following numerators are formed first:
-
-
- These are then divided by quantities specified in the verse.
-
- Place the arc and the successive results so obtained one below the other, and subtract each from the one above to get śara:
-
-
Transformation to current notation
Let θ be the angle subtended by the arc s at the centre of the circle. Then s = rθ and śara = r ( 1 - cos θ ). Substituting these in the last expression and simplifying we get
which gives the infinte power series expansion of the cosine function.
Madhava's reformulation for numerical computation
The last line in the verse ′as collected together in the verse beginning with stena, stri, etc.′ is a reference to a reformulation introduced by Madhava himself to make the series convenient for easy computations for specified values of the arc and the radius.As in the case of the sine series, Madhava considers a circle one quarter of which measures 5400 minutes (say C minutes) and develops a scheme for the easy computations of the śara′s of the various arcs of such a circle. Let R be the radius of a circle one quarter of which measures C. Then, as in the case of the sine series, Madhava gets
R = 3437′ 44′′ 48′′′.
Madhava's expression for śara corresponding to any arc s of a circle of radius R is equivalent to the following:
Madhava now computes the following values:
| No. | Expression | Value | Value in Katapayadi system Katapayadi system Kaṭapayādi system of numerical notation is an ancient Indian system to depict letters to numerals for easy remembrance of numbers as words or verses... |
|---|---|---|---|
| 1 | R × (π / 2)2 / 2! | 4241′ 09′′ 00′′′ | u-na-dha-na-krt-bhu-re-va |
| 2 | R × (π / 2)4 / 4! | 872′ 03′′ 05 ′′′ | mī-nā-ngo-na-ra-sim-ha |
| 3 | R × (π / 2)6 / 6! | 071′ 43′′ 24′′′ | bha-drā-nga-bha-vyā-sa-na |
| 4 | R × (π / 2)8 / 8! | 03′ 09′′ 37′′′ | su-ga-ndhi-na-ga-nud |
| 5 | R × (π / 2)10 / 10! | 05′′ 12′′′ | strī-pi-śu-na |
| 6 | R × (π / 2)12 / 12! | 06′′′ | ste-na |
The śara can now be computed using the following scheme:
- śara = (s / C)2 [ (4241′ 09′′ 00′′′) − (s / C)2 [ (872′ 03′′ 05 ′′′) − (s / C)2 [ (071′ 43′′ 24′′′) − (s / C)2[ (03′ 09′′ 37′′′) − (s / C)2 [(05′′ 12′′′) − (s / C)2 (06′′′) ] ] ] ] ]
This gives an approximation of śara by its Taylor polynomial of the 12'th order. This also involves one division, six multiplications and five subtractions only. Madhava prescribes this numerically efficient computational scheme in the following words (translation of verse 2.438 in Yukti-dipika):
The six stena, strīpiśuna, sugandhinaganud, bhadrāngabhavyāsana, mīnāngonarasimha, unadhanakrtbhureva. Multiply by the square of the arc divided by the quarter of the circumference and subtract from the next number. (Continue with the result and the next number.) Final result will be utkrama-jya (R versed sign).
In Madhava's own words
Madhava's arctangent series is stated in verses 2.206 – 2.209 in Yukti-dipika commentary (Tantrasamgraha-vyakhya) by Sankara VariarSankara Variar
Sankara Variar was an astronomer-mathematician of the Kerala school of astronomy and mathematics who lived during the sixteenth century CE...
. A translation of the verses is given below.
Jyesthadeva has also given a description of this series in Yuktibhasa
Yuktibhasa
Yuktibhāṣā also known as Gaṇitanyāyasaṅgraha , is a major treatise on mathematics and astronomy, written by Indian astronomer Jyesthadeva of the Kerala school of mathematics in about AD 1530...
.
Now, by just the same argument, the determination of the arc of a desired sine can be (made). That is as follows: The first result is the product of the desired sine and the radius divided by the cosine of the arc. When one has made the square of the sine the multiplier and the square of the cosine the divisor, now a group of results is to be determined from the (previous) results beginning from the first. When these are divided in order by the odd numbers 1, 3, and so forth, and when one has subtracted the sum of the even(-numbered) results from the sum of the odd (ones), that should be the arc. Here the smaller of the sine and cosine is required to be considered as the desired (sine). Otherwise, there would be no termination of results even if repeatedly (computed).
By means of the same argument, the circumference can be computed in another way too. That is as (follows): The first result should by the square root of the square of the diameter multiplied by twelve. From then on, the result should be divided by three (in) each successive (case). When these are divided in order by the odd numbers, beginning with 1, and when one has subtracted the (even) results from the sum of the odd, (that) should be the circumference.
Rendering in modern notations
Let s be the arc of the desired sine (jya or jiva) y. Let r be the radius and x be the cosine (kotijya).- The first result is
. - Form the multiplier and divisor
. - Form the group pf results:
- These are divided in order by the numbers 1, 3, and so forth:
-
-
- Sum of odd-numbered results:
- Sum of even-numbered results:
- The arc is now given by
- Sum of odd-numbered results:
-
Transformation to current notation
Let θ be the angle subtended by the arc s at the centre of the circle. Then s = rθ, x = kotijya = r cos θ and y = jya = r sin θ.
Then y / x = tan θ. Substituting these in the last expression and simplifying we get
.
Letting tan θ = q we finally have
Another formula for the circumference of a circle
The second part of the quoted text specifies another formula for the computation of the circumference c of a circle having diameter d. This is as follows.
Since c = π d this can be reformulated as a formula to compute π as follows.
This is obtained by substituting q = π / 6 in the power series expansion for tan-1 q.
Further reading
- K. V. SarmaK. V. SarmaK. V. Sarma was an Indian historian of science, particularly the astronomy and mathematics of the Kerala school.His doctoral thesis was at the Panjab University in 1977....
, A History of the Kerala School of Hindu Astronomy (Hoshiarpur, 1972). - A. K. Bag, Madhava's sine and cosine series, Indian J. History Sci. 11 (1) (1976), 54–57.
- D. Gold and D Pingree, A hitherto unknown Sanskrit work concerning Madhava's derivation of the power series for sine and cosine, Historia Sci. No. 42 (1991), 49–65.
- R. C. Gupta, Madhava's and other medieval Indian values of pi, Math. Education 9 (3) (1975), B45–B48.
- R. C. Gupta, Madhava's power series computation of the sine, Ganita 27 (1–2) (1976), 19–24.
- R. C. Gupta, On the remainder term in the Madhava–Leibniz's series, Ganita Bharati 14 (1–4) (1992), 68–71.
- R. C. Gupta, The Madhava–Gregory series, Math. Education 7 (1973), B67–B70.
- T. Hayashi, T. Kusuba and M. Yano, The correction of the Madhava series for the circumference of a circle, Centaurus 33 (2–3) (1990), 149–174.
- R.C. gupta, The Madhava–Gregory series for tan−1x, Indian Journal of Mathematics Education, 11(3), 107–110, 1991.
- "The discovery of the series formula for π by Leibniz, Gregory, and Nilakantha" by Ranjan Roy in :
- "Ideas of calculus in Islam and India" by Victor J Katz in :
- "Was calculus invented in India?" by David Bressoud in :
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