Most notable the sin of 45 degrees and 60 degrees......

Example: What is the missing length here?

• We know the Hypotenuse
• We want to know the Opposite

Sine is the ratio of Opposite / Hypotenuse:

sin(45°) = OppositeHypotenuse

Get a calculator, type in "45", then the "sin" key:

sin(45°) = 0.7071...

Now we know all of this:

0.7071... = Opposite 20