This week in pre-calculus 11, we learn about two laws you can use to find missing angles and side in triangles. These laws are called: Sine Law and Cosine Law and are primarily used in non-right triangles. Today I will be explain my preferred law, the sine law.

The “Sine Law” is used on a triangle when the triangle gives you two sides with one corresponding angle or two angles with on corresponding side. Below I have put two examples of this.

 

There are two different formulas when doing the Sine Law, one for finding an angle and another for finding the side

Angle:  = = 

Side:  =  = 

Example: find side A 

   

Step 1 – write out the formula using the given angles and sides 

=  = 

Step 2 – Because we are only trying to find side “a”, we can remove the “c” section of the formula 

= 

Step 3 – using algebra, we must isolate “a”, then use our calculators, to find the side measurement

a =

Once we do the calculations our finale answer is 8.285… which we can round up to 8