What is 3/7 as a reciprocal?

Evaluate cos2θ for cosθ = square root of 3/2

Which of the expressions (on the photo document i inserted) together represent all solutions to the following equation? 8cos(12x)+4=-4 *the answer should be in degrees.* > i would like for someone to explain the process to find the solutions for this.

Will give a: 122 b: 90 c: 48 d: 180