r = 380 cm, s = 390 cm and ∠Q=48°. Find the length of q

Question

 r = 380 cm, s = 390 cm and ∠Q=48°. Find the length of q, to the nearest centimeter.

Answer 1

use the Law of Cosines

c^2 = a^2 + b^2 - 2abCosC

r=380 cm, s = 390 cm Q = 48 degrees

q^2 = 380^2 + 390^2 -2(380)(390)Cos48

q = sqr(144400 + 152100 - 296,400(.66913))

q = sqr(296,500 - 198,330.31)

q = sqr98169.6883

q = 313.31

q= 313 cm. rounded to nearest integer