Hoppin' on the bandwagon (Dylan's blog)

9-3

Law of Sines

Law of sines is used for non right triangles and used only when you have an angle and an opposite leg value that you know.

The formula is : sin(angle1)/opp. leg 1 = sin(angle2)/opp. leg 2
*cross multiply to solve*

Ex. A civil engineer wants to determine the distance from points A and B to an inaccessible point C. From direct measurements the engineer knows: AB=25m, angleA=110 degrees, angleB=20 degrees. Find AB and BC.

B=20 degrees
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|-\
|--\
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|----\
|-----\
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A ? C =50 degrees
=110 degrees

sin 50/25=sin 20/AC

ACsin50/sin50=25sin20

AC=25sin20/sin50

AC=11.162 m

(time to skip long process for BC)

BCsin50=25sin110

BC=25sin110/sin50

BC=30.667 m