Use the Law of Cosines to determine the indicated angle Ass

Use the Law of Cosines to determine the indicated angle . (Assume a = 134.5, b = 60.4, and c = 156.5. Round your answer to the nearest degree.)

Solution

a²=b²+c²-2bc cos theta

134.5²=60.4²+156.5²-2(60.4)(156.5)cos theta

18090.25=3648.16+24492.25-18905.2 cos theta

10050.16=18905.2 cos theta

theta=58 degree