Если cosa=-1/3 и 180<a<270 то вычислите sina/2 cosa/2 tga/2

Question

Если cosa=-1/3 и 180

Answer 1

Cos(a) = cos^2(a/2) - sin^2(a/2)
cos^2(a/2) + sin^2(a/2) = 1

2*cos^2(a/2) = cos(a) + 1 = 2/3
cos^2(a/2) = 1/3, sin^2(a/2) = 2/3

{90 < a < 135}
cos(a/2) = - sqrt(1/3)
sin(a/2) = sqrt(2/3)
tg(a/2) = - sqrt(2)