Thread: Trigonometic Identities

Hi there .. I'm not sure how to approach this question and I would greatly appreciate it if someone could help me

Thanks a bunch .

Here's the question :

Prove the identity .

sin^4x - cos^4x = sin^2x - cos^2x

Originally Posted by asiankatt

Hi there .. I'm not sure how to approach this question and I would greatly appreciate it if someone could help me

Thanks a bunch .

Here's the question :

Prove the identity .

sin^4x - cos^4x = sin^2x - cos^2x

This is very simple.
Factor the left hand side,

Thus,

But,

Thanks a lot =) Now that I look at it .. it is really simple :S


.... I have another question if you dont mind answering it ...


Prove the indentity .

4/cos^2x - 5 = 4tan^2 x - 1

Originally Posted by asiankatt

Thanks a lot =) Now that I look at it .. it is really simple :S


.... I have another question if you dont mind answering it ...


Prove the indentity .

4/cos^2x - 5 = 4tan^2 x - 1

Express left hand side as,

Factor, and use reciprocal identity,

But,

Thus,