Пусть ctg x = - 7/24 найдите cos x/2

Sin²x=1: (1+ctg²x) = 1: (1+49/576) = 1:625/576=576/625

cos²x=1-sin²x=1-576/625=49/625

cosx=+-7/25

1) cosx=-7/25

cosx/2=√[ (1+cosx) / 2]

cosx/2=√[ (1-7/25) / 2]=√ (9/25) = 3/5

2) cosx=7/25=√[ (1+7/25) / 2]=√ (16/25) = 4/5