Definite Integration Question 252

Question: If $ f(x)=\int _{x^{2}}^{x^{4}}{\sin \sqrt{t}dt,} $ then $ {f}’(x) $ equals

Options:

A) $ \sin x^{2}-\sin x $

B) $ 4x^{3}\sin x^{2}-2x\sin x $

C) $ x^{4}\sin x^{2}-x\sin x $

D) None of these

Show Answer

Answer:

Correct Answer: B

Solution:

We have $ f(x)=\int _{x^{2}}^{x^{4}}{\sin \sqrt{t}}dt $

$ f’(x)=\frac{d}{dx}(x^{4})(\sin \sqrt{x^{4}})-\frac{d}{dx}(x^{2})(\sin \sqrt{x^{2}}) $

$ =4x^{3}\sin x^{2}-2x\sin x $ .