Math CentralQuandaries & Queries


A parallelogram has one side that is 12.0 cm and one angle that is 65°. The shorter diagonal is 25.0 cm. To the nearest tenth of a centimeter, how long is the other side of the parallelogram? Use the sine law.

Hi Felicia,


The law of sines tells us that

sin(65o)/25 = sin(BCA)/12

Solve for sin(BCA) and then use the inverse sine function to find the measure of the angle BCA. Since the sum of the angles on a triangle is 180o you can then find the measure of the angle CAB. Now use the law of sines again to find the length of BC.


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