Question

4cos(x)=-1+cos(x)

Answer 1

4cos(x)=-1+cos(x)At first let's gather cosines at the left part of the equation:

3cos(x)=-1
cos(x)=-1/3According to the general formulas for solutions of elementary trigonometric equations we obtain the following answer:

x=2pi*n+-cos^-1(-1/3)