Question

What is the exact value of cos theta = squareroot 2 over 2?

Answer 1

Ok, so you want us to find theta when $cos(\theta)=\frac{\sqrt{2}}{2}$
we know from our unit circle that when the angle is 45 degrees, cos(45°)=sin(45°)=$\frac{\sqrt{2}}{2}$
also we can find this by the special 45-45-90 triangle


when Θ=45°, cos(Θ)=$\frac{\sqrt{2}}{2}$