Why the answer is A, and why the others tempt you.
Using the product rule: dy/dx = (2x)(sin x) + (x²)(cos x) = 2x sin x + x² cos x. Option B incorrectly differentiates as if the product rule reduces to just multiplying derivatives. Option D has a sign error on the second term, and C omits the sin x factor from the first term.
Want this in Pidgin, Yoruba, Igbo or Hausa? Sign up free →
Practice more Further Mathematics questions
GCE Further Mathematics has thousands more questions like this — with Worked answers on every one.