Question

Вычислить значение sin(a), cos(a) если tg(a) = 2,4 и п<(a)<3п/2

Answer 1

$\cos^2\alpha=\dfrac1{1+\tan^2\alpha}=\dfrac1{1+2.4^2}=\dfrac1{6.76}\\ \cos\alpha=-\dfrac1{2.6}=-\dfrac5{13}\\ \sin\alpha=\tan\alpha\cdot\cos\alpha=-\dfrac{2.4}{2.6}=-\dfrac{12}{13}$