Solve cosx^4-sinx^4: Confirm My Answer?

[synergix]

Homework Statement

simplify cosx⁴-sinx⁴

The Attempt at a Solution

I got cos2x

does anybody want to solve this and let me know if I am right ?

 

[srvs]

Cos2x is correct.

 

[tiny-tim]

Homework Statement

simplify cosx⁴-sinx⁴

The Attempt at a Solution

I got cos2x

does anybody want to solve this and let me know if I am right ?

Hi synergix!

It's obviously cos2x …

if you're not sure, then either you didn't go the quick way (factorise a⁴ - b⁴ ), or you're not familiar enough with your trignonometric identities