Help with my trigonometry

[Ladowerf]

Trigga-brother-nometry.

Stop being a tribal little friend.

On-topic: Google math help websites.

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[Otis Da HousKat]

Stop being a tribal little friend.

On-topic: Google math help websites.

Stop being homophobic, you working class slob.

[mctwist]

They are only true if a=45

Proof (Using degrees):
sin(45) = cos(45)

Test:
a = 45
sin(4*45)-cos(4*45) = 1
sin(2*45)-cos(2*45) = 1
sin(90) = 1
cos(90) = 0
sin(180) = 0
cos(180) = -1
1-0 = 1
0-(-1) = 0+1 = 1

I cannot give you a formula, but this is just an easy way to give a small proof.

You might have had already your test, but it's good to know afterwards too.

[Ladowerf]

Stop being homophobic, you working class slob.

Oh, I apologize for using the word "friend". I didn't know it was a insult to gay people.

[skoposh]

So I have a test tomorrow and I'm stuck at one question.
I need to prove these two equations equal.
sin^4a-cos^4a = sin^2a-cos^2a

Now, I have no idea what I can do from here, or how can I proceed, help please?

This is a bit late but:
Google is better help than the Blockland fourms.
http://en.wikipedia.org/wiki/Proofs_of_trigonometric_identities

[Maor]

Yeah, a friend helped me solve it toady, I think I failed the test anyway so, thanks.