Jump to content

# Trig Proof

## Recommended Posts

How do I prove that:

(cosx-cos3x)/(sin3x-sinx)= tan2x?

##### Share on other sites

I suggest using the multiple angle formulas.

##### Share on other sites

How do I prove that:

(cosx-cos3x)/(sin3x-sinx)= tan2x?

do you want the proof?

##### Share on other sites

He may well want it but it's not this sites habit to give the answer. Giving hints and advice is better for th estudent.

##### Share on other sites

use the following identites

sin2x = 2sinxcosx

cos2x = 1-2sin^2x

cos3x = 4cos^3x - 3cosx

sin3x = 3sinx -4sin^3x - sinx

i did the proof its actually pretty simple.. good luck

## Create an account or sign in to comment

You need to be a member in order to leave a comment

## Create an account

Sign up for a new account in our community. It's easy!

Register a new account

## Sign in

Already have an account? Sign in here.

Sign In Now
×

• #### Activity

• Leaderboard
×
• Create New...

## Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.