Question

How do you verify cosθcos(−θ)−sinθsin(−θ)=1?

Answer 1

Answer:

Step-by-step explanation:

Always remember:

      cos(-θ)= cosθ      and    sin(-θ)= -sinθ

now substitute these in the equation:

cosθcos(−θ)−sinθsin(−θ)=1

cosθcosθ-sinθ(-sinθ) = 1

cos²θ+sinθsinθ = 1

cos²θ+sin²θ = 1

1 = 1   (Shown)