$x(x)=\frac{1}{1+x^2}$

$T_{2k}(x)=1-x^2+x^4-+...+(-1)^kx^{2k}$

f(x) = 1 / (1 + x^(2))
k = 0 (slider from 0 to 100, step 2)
g(x) = (1 - ((-x^(2)))^(k / 2 + 1)) / (1 + x^(2))
eq1: x = 1
eq2: x = -1