I would like to prove that

sinX^4 - cosX^4 + 2cosX^2

equals to 1 using sin^2 theta+ cos^2 theta=1 and a^2-b^2=(a-b)(a+b).

I am completely stuck though, and do not know where to begin. Any advice would be appreciated.

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- August 11th 2008, 01:03 AMPandoraTrigonometric proof
I would like to prove that

sinX^4 - cosX^4 + 2cosX^2

equals to 1 using sin^2 theta+ cos^2 theta=1 and a^2-b^2=(a-b)(a+b).

I am completely stuck though, and do not know where to begin. Any advice would be appreciated. - August 11th 2008, 01:09 AMflyingsquirrel
Hello

Note that . Can you factor this using ?

Hint (highlight to read) : * let a=(sin x)^2 and b=(cos x)^2 * - August 11th 2008, 01:11 AMChris L T521
- August 11th 2008, 11:46 AMPandoraThank you
Thank you both. It seems pretty clear now =) This forum is so efficient, and I will be definetly using it in the future.