Answer:
We have sinθ = 12/13
The method here is to figure out the value of θ
Using a calculator sin^(-1)(12/13) =67.38°
67.38° is in quadrant 1 so we must substract 67.38° from 180° wich is π
- 180-67.38= 112.61° ⇒ θ= 112.61°
Now time to calculate cos2θ and cosθ using a calculator
- cosθ = -5/13
- cos2θ = -0.7
The values we got make sense since θ is in quadrant 2 and 2θ in quadrant 3
