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nhoc_smile97


a) [TEX] sin^2 2x - sin^2 3x = 0 [/TEX]
b) [TEX] cos^2 (2x - \frac{pi}{3}) - cos^2(x+\frac{pi}{4} = 0 [/TEX]
c) cos5x cosx _ sin6x sin2x = cos 7x
d) cos4x + cos2x = sinx - sin5x
b) [TEX] cos^2 (2x - \frac{pi}{3}) - cos^2(x+\frac{pi}{4} = 0 [/TEX]
c) cos5x cosx _ sin6x sin2x = cos 7x
d) cos4x + cos2x = sinx - sin5x