How do you find the derivative of # y = cos(2x)#?

Question

1127 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2015-12-27T07:27:16

#frac{dy}{dx} = -2sin(2x)#

Let #u = 2x#

#frac{du}{dx} = 2#

#frac{dy}{dx} = frac{d}{dx}(cos(2x))#

#= frac{d}{dx}(cos(u))#

#= frac{d}{du}(cos(u))*frac{du}{dx}#

#= (-sin(u))*(2)#

#= -2sin(2x)#