Created
July 5, 2015 15:49
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| cos 4x = 8(cos x)^4 - 8(cos x)^2 + 2 - 2 + 1 | |
| cos 4x = [ 8(cos x)^4 - 8(cos x)^2 + 2 ] - 1 | |
| Sectioned off part of the right side, then factored it | |
| cos 4x = [2 ( cos x )^2 - 1] [4 (cos x)^2 - 2] - 1 | |
| cos 4x = [2 ( cos x )^2 - 1] 2*[2 (cos x)^2 - 1] - 1 | |
| Identity: 2 (cos x)^2 - 1 = cos 2x | |
| cos 4x = cos 2x * 2 cos 2x - 1 | |
| cos 4x = 2 (cos 2x)^2 - 1 | |
| Using the identity again... | |
| cos 4x = cos 4x |
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