Question

Find m\angle Cm∠Cm, angle, C.
Round to the nearest degree.

Help Course Challenge

Answer 1

use cosine rule

15²=14²+11²-2×14×11cosC

225-196-121=-308cosC

-92/-308=cosC

cosC=23/77

C=cos-¹(23/77)=72.62° is your answer

Answer 2

Hello,

1. Since Angle C has the longest side for this triangle, it will have the largest degree value.

2. Use the Law of Cosines and inverse properties of “theta” to solve for Angle C. (Ensure that the calculator used is in “degree mode”, not “radian mode”.

c^2 = a^2 + b^2 - 2(a)(b)(cos (C))
15^2 = 11^2 + 14^2 - 2(11)(14)(cos(C))
225 - 317 = -2(11)(14)(cos(C))
-92 / -2(11)(14) = cos(C)
cos(C) becomes ->> cos^-1[92 /-2(11)(14)] = 72.62° ->> to the nearest degree is 73°

The answer for angle C, 73°, is logical because the triangle in the picture represents a 60-60-60 triangle, known as an equilateral triangle.

Good luck to you!