BLAOW!!!! David's Blog.

Section 9-3 was about Law of Sines, which was kind of easy.

There are two rules that you NEED to know though
First Law of Sines can only be used on non right triangles
Second it can only be used when you have an angle and opposite leg that are known.

Other than that all you need to know is the very simple formula for it.

sin(angle)/opposite leg = sin(angle 2)/opposite leg 2

Just cross multiply and solve.

For instance: A triangle FTL has three angles, F=110 T=20 L=50, and leg FT = 25 meters. Find legs FL and LT.

L50



? ?



F110 20T
25 m


Sorry about the bad visual but I think you get the point.

Okay so first we're going to find FL. Our triangle is not right and we have an angle L and an opposite leg of L so we are good to go.

soo sin(50)/25 sin(20)/FL
cross multiply and we get FL sin 50= 25 sin 20
solve FL = 25 sin 20/sin 50
plug into a calculator FL = 11.162

now for LT

sin(50)/25=sin(110)/LT
LT sin 50= 25 sin 110
LT = 25 sin 110/sin 50
LT = 30.667


Easy enough right?