use the law of cosines to solve the triangle a=55, c=72, b=25

Answer 1

cosB = (a^2 + c^2 - b^2) / 2ac,
cosB = ((55)^2 + (72)^2 - (25)^2/7920 = 7584 / 7920 = 0.9576.
B = 16.7 deg.