Choose the number of times you want to expand the infinite series. As an example, choose 4 times for n = 0, 1, 2 and 3
Calculate the individual values of the series for each value of n using the formula: (-1)^n/(2n + 1)!(x^(2n +1)). For example:
For n = 0
[(-1)^n/(2n + 1)!(x^(2n +1))] = SUM [(-1)^0/(2(0) + 1)!(x^(2(0) +1))] = 1/1 * x = x.
For n = 1
[(-1)^n/(2n + 1)!(x^(2n +1))] = [(-1)^1/(2(1) + 1)!(x^(2(1) +1))] = -1/(3!)x^3 = -X^3/3! = -x^3/6.
For n = 2
[(-1)^n/(2n + 1)!(x^(2n +1))] = SUM [(-1)^2/(2(2) + 1)!(x^(2(2) +1))] = 1/(5!)x^5 = x^5/5! = x^5/120
For n = 3
[(-1)^n/(2n + 1)!(x^(2n +1))] = SUM [(-1)^3/(2(3) + 1)!(x^(2(3) +1))] = -1/(7!)x^7 = -x^7/7! = -x^7/5040
Add the individual values together. In this example:
sinx = SUM [(-1)^n/(2n + 1)!(x^(2n +1))] = x - x^3/6 + x^5/120 - x^7/5040 ........