How do you prove ...

sin(x+y)sin(x-y) = cos ^2y - cos ^2x

1 + cos x= cot x / 2

sin x

tan(x+y)tan(x-y) = sin^2x - sin^2y / cos^2x -sin^2y

(if anyone can tell me the math BBCode that would be nice too)

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- November 5th 2007, 02:52 PMfinalfantasytrig identity help.
How do you prove ...

sin(x+y)sin(x-y) = cos ^2y - cos ^2x

__1 + cos x__= cot x / 2

sin x

tan(x+y)tan(x-y) = sin^2x - sin^2y / cos^2x -sin^2y

(if anyone can tell me the math BBCode that would be nice too) - November 5th 2007, 05:38 PMThePerfectHacker
- November 6th 2007, 04:42 AMtopsquark