Find the derivative of the trigonometric function.
f(x)=-x+tanx

Question

Find the derivative of the trigonometric function.
f(x)=-x+tanx

mimi_x3 · Answer

Well, the derivative of tanx = sec^2x. 
so..
$$f'(x) = -1 + \sec^2x$$

anonymous · Answer

hmmmm how do i knw the derivative of tanx = sec^x?

directrix · Answer

mimi_x3 · Answer

Well, you have to like memorise the derivative of it.

anonymous · Answer

and the book says tan^2x so i assume sec^2x -1 = tan^2x

mimi_x3 · Answer

Yes. Its a trig identity.

anonymous · Answer

oh i belive mimi just asking for my knowledge

anonymous · Answer

dont want someone just doing my homework for me

anonymous · Answer

lol

anonymous · Answer

id rather learn then just write down the correct answer :)

directrix · Answer

You have to know the basic trig identities. Just a few of them and they are related.

anonymous · Answer

i am just wondering why my book doesnt tell me this before asking this question

anonymous · Answer

oh i know the trig identities but not the derivatives

anonymous · Answer

like i know 1-sin^2 = cos^2

directrix · Answer

anonymous · Answer

but that didnt teach me the derivative of cos^2

anonymous · Answer

thanks i looked at it :)

anonymous · Answer

so i need to memorize these too?