Hey :o !
Could you help me at the following exercise?
$k, n \in \mathbb{N}$
$f(x)=cos(k \pi x), x \in [0,1]$
$x_i=ih, i=0,1,2,...,n, h=\frac{1}{n}$
Let $p \in \mathbb{P}_n$ the Lagrange interpolating polynomials of $f$ at the points $x_i$.
Calculate an upper bound of the maximum error...