Please help I’m struggling bad bad please help no links

Evaluate cos2θ for cosθ = square root of 3/2

Sanya noticed that the temperature was falling at a steady rate of 1.4 degrees every hour from the time that she first checked her outdoor thermometer. by 6 a.m., the temperature had fallen 21 degrees. which expression can you use to find how many hours earlier she had first checked the thermometer?

1.based of the diagrams what is the the value of x? 2.how would you verify your answer for x