Question

Which equation could be used to solve for the length of side c, given a = 5, b = 12, and C = 72°?

Answer 1

The value of the length of the side C is 11.49.

Explanation:

Cosine formula is applicable.

c² = a² + b² -2abcos(C)

substitute the values:

c² = (5)² + (12)² -2(5)(12)cos(72)

= 25 + 144 - 2 (60) (0.309)

= 169 - 37.08

c² = 131.92

square root both sides:

c = sqrt(131.92)

C = 11.49