28.4 Let f(x)= x2 sin x 1 for x =0 and f(0)=0.(a) Use Theorems 28.3 and 28.4 to show f is differentiable at eacha =0 and calculate f (a). Use, without proof, the fact thatsin x is differentiable and that cos x is its derivative.(b) Use the definition to show f is differentiable at x =0 andf (0)=0.(c) Show f is not continuous at x =0