Question

One more thing, how will I get the derivative of cos2(theta)?

Answer 1

know the chain rule ?

Answer 2

\[\cos^2(\theta)\] correct? Follow what @hartnn said.

Answer 3

i think its \(\cos 2 \theta\)

Answer 4

no, it was actually cos2(theta)

Answer 5

I think it might be more clear if you put the 2 inside the parenthesis, just for future reference, but either way, you would still use the chain rule.

Answer 6

so do u know derivative of cos theta ?

Answer 7

it's -sin theta

Answer 8

so do u know how to use chain rule to get derivative of cos 2theta ?

Answer 9

\(f(g(x))' = f'(g(x))\times g'(x)\)
so, \((\cos 2\theta )'=(-\sin 2\theta )\times (2\theta)'=....?\)

Answer 10

ahhh...it's basically the chain rule

Answer 11

I though I would have to use some trig identity

Answer 12

thats what i first asked :P
so what u got ?

Answer 13

if u got -2sin 2theta, then its correct

Answer 14

thanks! I did :)