Question

Derive d^2y/dx^2 y=sinxcosx

I get -2sinxcosx-2cosxsinx

But it says the answer is -4sinxcosx how?

Answer 1

Combine like-terms silly!

Answer 2

\[\Large\rm -2(stuff)-2(stuff)=-4(stuff)\]

Answer 3

Keep in mind that since multiplication is `commutative` (you can multiply in any order), it means that sinx cosx = cosx sinx

So your second term is really -2sinx cosx

Answer 4

Thank you awesome person!