Homework Help

Prove each identity. 1.->  cos^2x-sin^2x=2cos^2x-1 identites include- ...

user profile pic

sasuke24 | Student, Undergraduate | (Level 2) Honors

Posted December 8, 2012 at 10:38 PM via web

dislike 0 like

Prove each identity. 1.->  cos^2x-sin^2x=2cos^2x-1 

identites include- 

cscx=1/sinx , secx=1/cosx , cotx=1/tanx , tanx=sinx/cosx , cotx=cosx/sinx , sin^2x+cos^2x=1

1 Answer | Add Yours

user profile pic

lfryerda | High School Teacher | (Level 2) Educator

Posted December 9, 2012 at 12:18 AM (Answer #1)

dislike 1 like

If you have more than one question you need to make separate posts.

In order to prove this identity, you need to start with one side, and then using existing identities, end up at the other side of the identity.

`LS=cos^2x-sin^2x`   use `sin^2x+cos^2x=1`

`=cos^2x-(1-cos^2x)`   remove brackets

`=cos^2x-1+cos^2x`  collect like terms

`=2cos^2x-1`

`=RS`

The identity has been proven.

Join to answer this question

Join a community of thousands of dedicated teachers and students.

Join eNotes