9-1

This week I am going to teach you how to use sine, cosine, and tangent to find side the lengths and angle measures of a right triangle. This is a very easy thing to do.
There are three formulas that help us to do this:
• Sin x = opposite / hypotenuse
• Cos x = adjacent / hypotenuse
• Tan x = opposite / adjacent
The word SOHCATOA is used to help us remember these three formulas.
These formulas will ONLY work on RIGHT triangles. Whenever you find the side lengths, you NEVER use the 90 degree angle.
Now it is time to show you an example.
EXAMPLE: Find x and y (picture at top)
First we are going to find side length x. You are given the angle 35 degrees and the hypotenuse, 7. You would use sin, which gives you sin 35 degrees=x/7. You would then multiply both sides by 7, which gives you 4.015. So, x=4.015.
Next we are going to find side length y. This time you would use cosine, which gives you cos 35 degrees=y/7. When you multiply both sides by 7, it gives you y=5.734.