Problema Solution

If the sides of a parallelogram and an included angle are 6, 10 and 100 degrees respectively, find the length of the shorter diagonal

Answer provided by our tutors

Let

a = 10

b = 6

the angle B = 100

d = the shorter diagonal

Angle A + Angle B = 180

Angle A = 180 - Angle B

Angle A = 180 - 100

Angle A = 80

Using the The Law of Cosines we have

d^2 = a^2 + b^2 - 2ab cos(Angle A)

d^2 = 6^2 + 10^2 - 2*6*10*(cos(80))

by solving we find

d = 10.73

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The length of the shorter diagonal is 10.73.