Question

PLEASE HELP ME THANK YOU. ALSO PLEASE INCLUDE EXPLANATION

Answer 1

Given

the lengths of the 3 sides of a triangle

Find

the angle opposite the longest side

Solution

Strategy: make use of the Law of Cosines, which relates an angle and the three sides of a triangle.

... a² = b² + c² -2bc·cos(A)

... cos(A) = (b² + c² - a²)/(2bc) . . . . . . . solve for cos(A)

... A = arccos((b² + c² - a²)/(2bc))

Fill in the given values and evaluate.

... A = arccos((55² + 50² - 90²)/(2·55·50)) = arccos(-2575/5500)

... A ≈ 117.9°