precal 2

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

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  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.

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