4 sin^2 x - 4 cosx -1 =0

Question

4 sin^2 x - 4 cosx -1 =0

Answer 1

4-4cos^2x-4cosx-1=0            |cosx|≤1
-4cos^2x-4cosx+3=0 *(-1)
4cos^2x+4cosx-3=0
D=64
cosx=1/2
cosx=-12/8 не уд т.к. cosx<-1<br>
cosx=1/2
x=+-п/3 + 2пn. n-целое