Question

Pls help <3 Triangle ABC has side lengths a = 79.1,b = 54.3, and c = 48.6 What is the measure of angle A

a.100.3°
b.42.5°
c.88.9°
d.37.2

Answer 1

100.3 degrees.

Explanation:

By the Cosine Rule:

a^2 = b^c + c^2 - 2bc cos A

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

= (79.1^2 - 54.3^2 - 48.6^2) / (-2*54.3 * 48.6)

= -0.1793

A = 100.329 degrees