Question

Выражение: (sin^2 a+ tg^2 a sin^2 a) ctg а

Answer 1

$(sin^{2} \alpha + tg^{2} \alpha * sin^{2} \alpha )*ctg \alpha = \\ =sin^{2} \alpha ( 1 + tg^{2} \alpha )*ctg \alpha = sin^{2} \alpha * \frac{1}{cos^{2} \alpha} * ctg \alpha = tg^{2} \alpha * ctg \alpha = tg \alpha$