Question

Don't Understand?....
(Pre-Cal)
Evaluate for Sin 2u, cos 2u, tan 2u... if Tan u= -4 ?

How do I solve for Tan -4? what formula?

Answer 1

am i supposed to start with sin -4/cos -4?

Answer 2

do i have to use a half angle formula to find the result for sin or cos?

Answer 3

use below

\[\sin(2u) = \frac{2\tan (u)}{1+\tan^2 (u)}\]

\[\cos(2u) = \frac{1-\tan^2 (u)}{1+\tan^2 (u)}\]

Answer 4

how did you derive the first formula?

Answer 5

see
https://answers.yahoo.com/question/index?qid=20081106094912AAwnY0Z

Answer 6

im still confused on how to find the values?

Answer 7

nevermind i think i got it. thank you

Answer 8

np :) just plugin the tanu value and simlify