I don't understand, what do you use sin, cos and tan for?

Sin, cos and tan are functions that help you work out either, the missing angle or one of the missing lengths of a side in a right angle triangle.To work out the missing angle you need two side lengths, depending on which lengths you have depends on whether you use sin, cos or tan. For example, if you have the hypotenuse (the longest side) and the side opposite to the angle missing, you would use sin. The equation is always, function(angle) = side / other side, so in this case - sin(angle) = opposite/hypotenuse. To rearrange this, on your calculator these is a button which looks like sin^-1, this will be used as rearranging the equation to find the angle will look like angle = sin^-1(opposite/hypotenuse).To help you remember which function is used when, try to remember this funny sounding word SohCahToa, it stands for - Sin opposite hypotenuse, Cos adjacent hypotenuse and Tan opposite adjacent. If you have the angle but you are missing a side, you can always use the equation and rearrange it to find the side.