- #1

madmike159

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## Homework Statement

prove that, (cos(3x) - cos (7x)) / (sin(7x) + sin(3x)) = tan(2x)

prove that, cos(3x) = 4cos^3(x) - 3cos(x)

## Homework Equations

tan(x) = sin(x)/cos(x) must come into the first one

## The Attempt at a Solution

tried seperating the fraction so there is only one cos term on top, but I don't know how to deal with the sin terms on the bottom.

I haven't got a clue for the second one