This week, I have learned how to find the missing angle or missing length by using cos law.

There are 2 ways to use the cos law.

- To find the missing angle
- To find the missing lenght

To find the missing angle, we use : cosC=

To find the missing length, we use : cos C

Let’s try an example

We know that angle C is 37, and we are looking for the length C.

Lets write down every thing in the formula.

Length:

cos C

cos 37

C= 3.9 cm

Lets try another example.

Angle:

cosC=

cos X= 2(6)(5)

X= 2(6)(5) * cos^-1

X=93