Question

Given that y=5 sin2x, then dy/dx=
a) -5 cos2x
b) -10 cos2x
c) 5 cos2x
d) 10 cos 2x

I think it's C but can someone please explain.

Answer 1

It's not C.

\[y=5\sin(2x),\text{ so by the chain rule}\\
\frac{dy}{dx}=5\frac{d}{dx}\sin(2x)\\
\frac{dy}{dx}=5\cos(2x)\cdot\frac{d}{dx}(2x)\\
\frac{dy}{dx}=\cdots\]

Answer 2

So it's D. Thank you.

Answer 3

You're welcome