Question

1. \cos a

Explanation:

Step1: Recall cosine definition

For angle $A$ in right triangle, $\cos A = \frac{\text{adjacent side}}{\text{hypotenuse}}$

Step2: Identify sides for $\cos A$

Adjacent to $A$: $AB = 36$, Hypotenuse: $AC = 45$

Step3: Substitute and simplify

$\cos A = \frac{36}{45} = \frac{4}{5}$

Answer:

$\frac{4}{5}$