Question

In triangle ABC, AC=13, BC=84, and AB=85. Find the measure of angle C

Answer 1

90degrees

Explanation:

To get the measure of angle C, we will use the cosine rule as shown;

AB² = AC²+ BC² - 2(AC)(BC)cos C

85² = 13²+ 84² - 2(13)(84)cos C

7225 = 169 + 7056 - 2184cosC

7225 - 7225 = -2184cosC

0 = -2184cosC

cosC = -0/2184

cosC = 0

C = arccos0

C = 90degrees

Hence the measure of angle C is 90degrees