Question

Найдите значение выражения cos2x, если cosx=-0,6.

Answer 1

1-2sin^2 x = 3/5;
sin^2 x = 1/5
sin x = 1/sqrt(5)
cos x = 2/sqrt(5);
tg x = 0,5
ctg x = 2;

Answer 2

cos2x=cos^2x-sin^2x

sin^2x=1-0.36

sin^2x=0.64

cos2x=(-0.6)^2-0.64=-0.28