In the given figure, cos θ is equal to:

By observing the triangle PQR carefully . we find that

B = 12 & H = 13

By using pythagoras theorem ,

P² + B² = H²

P² + 12² = 13²

P² = 169 - 144

P² = 25

P = 5

cosθ = \(\frac{B}{H}\)

= \(\frac{5}{13}\)  { in case angle is θ , B = 5 }