prove that cos^2x-sin^2x=1-2sin^2x?

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prove that cos^2x-sin^2x=1-2sin^2x?

2007-05-17 11:55:13 · 3 answers · asked by jermaine d 1 in Science & Mathematics ➔ Mathematics

3 answers

Use the trig identity: sin^2x + cos^2x = 1 to replace the 1 on the right side of the equation.

So you get:

cos^2x - sin^2x = sin^2x + cos^2x - 2sin^2x

Simplify and see that both sides of the equation are the same.

2007-05-17 12:00:04 · answer #1 · answered by dave r 2 · 0⤊ 0⤋

If you add 2 sin^2 x to both sides, you wind up with the basic Phythorean identity with sine and cosine.

2007-05-17 18:59:15 · answer #2 · answered by cattbarf 7 · 0⤊ 0⤋

cos^2x-sin^2x
= 1-sin^2x-sin^2x
= 1-2sin^2x

2007-05-17 19:00:29 · answer #3 · answered by sahsjing 7 · 0⤊ 0⤋