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Sa se verifice egalitatile:
a)sin4x+2sin2x=4sin2x*[tex] cos^{2} x[/tex]
b)[tex](7+ cos4x) ^{2} =32(1+ sin^{8} x+ cos^{8} x)[/tex]
c)[tex] \frac{sin2a}{1+cos2a} * \frac{cosa}{1+cosa} =tg \frac{a}{2} [/tex]
d)[tex] \frac{1-2tga*ctg2a}{1+2ctga*ctg2a} =tg^{2}a [/tex]