Question

как это решить?
how to solve this?

Answer 1

$displaystyle frac{cosa}{sina} -frac{sina}{cosa} -frac{2sin2a}{cos2a} =\\ =frac{cos^2a-sin^2a}{sinacosa} -frac{2sin2a}{cos2a} =\\ =frac{2cos2a}{sin2a} -frac{2sin2a}{cos2a} =\\ =frac{2cos^22a-2sin^22a}{sin2acos2a} =\\ =frac{4cos4a}{sin4a} =frac{4}{tg4a} =\\=frac{4}{-frac{2}{5}} =-frac{4*5}{2}=-10$