Question

Найдите cos a, если sin a = 7/25 и a принадлежит ( п/2;п)

Answer 1

A∈(pi/2;pi)⇒cos(a)<0
sin(a)=7/25
sin^2(a)=49/625
cos^2(a)=1-sin^2(a)=1-49/625=(625-49)/625=576/625
cos(a)= -24/25