Question

d/dx(cos2x)=??

Answer 1

-2sin(2x)

Answer 2

use first principal

Answer 3

?

Answer 4

ok thanks

Answer 5

lim h-> 0 of (cos(2(x+h)-cos(2x))/h like this?

Answer 6

yes

Answer 7

hmm maybe the double angle identity would help, but i forget it.

Answer 8

Simple chain rule...
Derivative of the outside function is -sin(2x)
times the derivative of the inside function which is 2

Answer 9

they dont know derivative rules yet, he needs to use the quotent rule
lim h-> 0 of (cos(2(x+h)-cos(2x))/h like this?