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Cel mai inteligent răspuns!
2014-02-17T21:52:55+02:00
Se foloseste de trei ori formula sin 2a=2 sina·cosa (prima data a=4x, a doua oara a=2x si a treia oara a=x)

\dfrac{\sin8x}{8\sin x}=\dfrac{2\sin4x\cos4x}{8\sin x}=\dfrac{2\sin2x\cos2x\cos4x}{4\sin x}=

=\dfrac{2\sin x\cos x\cos2x\cos4x}{2\sin x}=\cos x\cos2x\cos4x
3 5 3