have a look at this
It even uses the cosine as an example.
suppose cos x is to be approximated by an interpolating polynomial of degree n using n+1 equally spaced nodes in interval [0,1].How accurate is the approximation(express in terms of n)
here i took h=1/n
but i know the formulas for maximum error bound of linear and quadratic interpolation now the polynomial of degree n is creating problem
please help