Question

Решить уравнение 2cos^2 x+5sinx-4=0

Answer 1

2(1-sin^2x)+5sinx-4=0

2-2sin^2x+5sinx-4=0

2sin^2x-5sinx+2=0

(5+-sqrt(25-16))/4

(5+-3)/4

-1<=sinx<=1

sinx=1/2

x1=П/6+2Пk

x2=5/6П+2Пk