Question

If the length of side a is 12 centimeters, m

∠B
= 36°, and m
∠C
= 75°, what is the length of side b? Round your response to two decimal places.

Answer 1

Side B would be about 7.56 if you use trig.

Answer 2

Answer: b = 7.56 cm .
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All angles in a triangle add up to 180 ;

so m∠A = 180 - (75 + 36) = 180 - 111 = 69 ;

Note: The law of sines:

(sin A) / a = (sin B) / b = (sin C) / C.
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We have solved for m∠A ; which is: 69;

(sin A) / a = (sin B) / b ; solve for "b" ;
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(sin A) / a = (sin 69) / 12 cm ;

(sin B) / b = (sin 36) / b ; solve for "b" .

(sin 69) / 12 cm = (sin 36) / b ; solve for "b" ;
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b sin 69 = 12 sin 36 ;

Divide each side of the equation by "sin 69" ; to isolate "b" on one side of the equation; and to solve for "b" ;
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{b sin 69} / sin 69 = {12 sin 36} / sin 69 ;

b = (12 sin 36) / sin 69 = 7.5552387639166787

b = 7.56 cm .
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