Given a = 108 degree, b=9 and c = 15, use the law of cosines to solve the triangle for the value of A. Round answer two decimal places.

a. 19.13

b. 14.92

c. 19.73

d. 18.53

c. 19.73

Step-by-step explanation:

The Cosine rule shows states that:

a²=b²+c²-2bcCos A, where a, b and c are the sides of the triangle and A is the angle at vertex A.

A=108°

b=9

c=15

Substituting with the values above gives:

a²=9²+15² - (2*9*15 Cos 108)

a²=389.4346

a=19.73