Talk:Difference of Fourth Powers of Cosine and Sine

Or you could use cos^4 - sin^4 = (cos^2 - sin^2)(cos^2 + sin^2), since (cos^2 + sin^2) = 1. --Captain Pedant

Thanks for noting that. Proof has been added; it's considerably simpler. FFR, it's helpful for keeping track of who says what to sign your posts on talk pages; this is generally done by putting --~~~~. --Lord_Farin (talk) 13:21, 11 January 2013 (UTC)