How do you find the derivative of

Question

y=5sin(-x)

Answer 1

use the chain rule

y = f(u(x))
y' = df/du * du/dx

here, u = -x, so

dy/dx = 5cos(-x)(-1) = -5cos(-x)
which, since cos(-x)=cos(x), is -5cos(x)

Or, you can note that

sin(-x) = -sin(x), so what you have is

y = -5sin(x)
y' = -5cos(x)