С решением, пожалуйста5cos2x-14cos2x+8 = 0 3cos2x-14cosx+7 = 0 11sin2x+6cos2x+6 = 0

Question

С решением, пожалуйста
5cos2x-14cos2x+8 = 0
3cos2x-14cosx+7 = 0
11sin2x+6cos2x+6 = 0

Answer 1

3 cos2x - 14 cosx + 7 = 0 
3 cos2x - 14 cosx = -7 
cos(x)(3cos(2)-14)=-7 
-11.001827cos(x)=-7 
cos(x)=-7/-11.001827 
cos(x)=0.636258 
x=50.489