Question

n ΔABC, if the length of sides a, b, and c are 3.5 centimeters, 5.5 centimeters, and 6 centimeters respectively, what is m∠C to two decimal places?

Answer 1

We are given with three sides with measurements such as below:
a = 3.5 cm 
b = 5.5 cm
c = 6 cm
We are asked to solve for m∠C. To solve this we need to apply Law of Cosines such as below:
cos C = a²+b² - c² /2ab
cos C = 3.5² + 5.5² -6² / (2*3.5*5.5)
cos C = 0.16883
C = 80.28°