Need help on these two math problems please 1 and 2

Evaluate cos2θ for cosθ = square root of 3/2

The circle below is centered at the point (3, 1) and has a radius of length 2. what is the equation?

The perimeter of △cde is 55 cm. a rhombus dmfn is inscribed in this triangle so that vertices m, f, and n lie on the sides cd , ce , and de respectively. find cd and de if cf=8 cm and ef=12 cm. the answer is not cd=20 and de=15. i have tried that one, it does not work.