8 (sin^2) x - 12 cos x = - 7

Question

8 (sin^2) x - 12 cos x = - 7

Answer 1

8-8cos²x-12cosx+7=0
cosx=a
8a²+12a-15=0
D=144+480=624
a1=(-12-4√39)/16⇒cosx=(-3-√39)/4<-1 нет решения<br>a2=(-3+√39)/4⇒cosx=(-3+√39)/4⇒x=+-arccos[(-3+√39)/4]+2πn,n∈z