Law of Sines

The Law of Sines helps us solve for non-right triangles. It is simply a proportion that we need to solve for.

or

Capital letters always represent angles.
Lowercase letters always represent sides.

Angle is always opposite side .
Angle is always opposite side .
Angle is always opposite side .

Solving for a Side: Side – Angle – Side

Since we’re solving for a side, put the unknown side on the top-left fraction, then solve for .

Solving for an Angle: Side – Side – Angle

Since we’re solving for an angle we must use an inverse sine to finish the problem. Just like above, we put the unknown in the top left of the fraction.

Proof

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