Question

4sin^2x-4cosx=1. решите уровнение

Answer 1

=4(1-cos^2x)-4cos x- 1=0 <=> 4-4cos^2x- 4cos x -1=0 <=>

-4cos^2x-4cos x+3=0 | * (-1) 

4cos^2x+4cos x -3=0

 cos x=1

 cos x=-3