Question

1) 2cos²x+sinx-1<0

2) 2sin²x-5cosx+1>0​

Answer 1

Ответ:

2cos²x-sinx-1=0

2(1-sin²x)-sinx-1=0

-2sin²x-sinx+1=0

2sin²x+sinx-1=0

sinx=y

2y²+y-1=0

y₁=½,y₂=-1