Question

What is the measure of angle a?​

Answer 1

38°

Explanation:

Using the Cosine rule in Δ ABC

cos A =
`(b^2+c^2-a^2)/(2bc)`

where a, b and c are the sides of the triangle.

Here a = 5, b = 3 and c = 7 , thus

cos A =
`(3^2+7^2-5^2)/(2(3)(7))` =
`(9+49-25)/(42)` =
`(33)/(42)` , thus

∠ A =
`cos^(-1)` (
`(33)/(42)` ) ≈ 38°