Question

Вычислите:

$1+cos(2a)$

если $sin(a)=-0,6$

Answer 1

$1+cos^{2} ( \alpha )-sin^{2} \alpha$
$sin^{2} \alpha = 0.36$
$cos^{2} \alpha = 1- sin^{2} \alpha =1-0.36=0.64$
$1+cos^{2} ( \alpha )-sin^{2} \alpha =1+0.64-0.36=1.28$