1/f - 1/u = 1/v then f
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<h3>Answer: angle B = 47 degrees</h3>
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Work Shown:
Use law of cosines to find angle B
b^2 = a^2 + c^2 - 2*a*c*cos(B)
9^2 = 6^2 + 12^2 - 2*6*12*cos(B)
81 = 36 + 144 - 144*cos(B)
81 = 180 - 144*cos(B)
81 - 180 = -144*cos(B)
-99 = -144*cos(B)
-144*cos(B) = -99
cos(B) = (-99)/(-144)
cos(B) = 0.6875
B = arccos(0.6875)
B = 46.5674634422102
B = 47 when rounding to the nearest whole number
Make sure your calculator is in degree mode.
arccos is the same as inverse cosine often labeled on calculators.
