Question

A function h is defined by h:R^2\{(0,0)}. h is given by h(x,y)=(cos(x)-cos(y))/(x^2+y^2). Additional a function H is defined by H(x):=lim(y->0)h(x,y)
Determine H(x) and evaluative whether the function H is continuous of x and what does this say about the opportunities to choose a value c=h(0,0) so that h become continuous on the whole R^2