I'm trying to find the second derivative of h(x)= x^2 + cos(kx)
My answer for h'(x) is 2x - ksin(kx) but I'm not sure if that's right.
Then the answer I got for h''(x) was h''(x) = 2 - k^2cos(kx) but I'm pretty sure that's wrong based on the graph I was given.
Is my answer for the first derivative right? Thanks!