Find Power Series and interval of convergence of g(x) = x^{-2} ln(1+x^{2})
ln(1+z) = Σn=1,∞ (-1)^{n-1} z^{n}/n so
g(x) = ∑n=1,∞ (-1)^{n-1} x^{2(n-1)}/n
To get an idea about the radius of curvature, consider what happens for purely imaginary values of x,that is let x = i b for real b.
g(i b) = ∑n=1,∞ b^{2(n-1)}/n for b = 1 this series diverges logarithmically. for b >1 the divergence is even faster.
So the radius of curvature is |x| <1
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