Question

What is the value of cos θ if the terminal side of θ and the unit circle intersect at point ( sqrt(2)/2 ,- sqrt(2)/2 )

Answer 1

cos θ equals the x-coordinate on the unit circle, so cos θ = √2/2. (This corresponds to θ = 315° = 7π/4, or θ = −π/4, plus full rotations.)