Question

Реееешшшеееннниииеее???

Answer 1

$frac{tg2a}{tg4a-tg2a}=frac{sin2a}{cos2acdot (frac{sin4a}{cos4a}-frac{sin2a}{cos2a})}=frac{sin2acdot cos4acdot cos2a}{cos2acdot (sin4acdot cos2a-sin2acdot cos4a)} =\\= frac{sin2acdot cos4a}{sin(4a-2a)} = frac{sin2acdot cos4a}{sin2a} =cos4a$