# The lengths of the sides of a triangle are 7, 8 and 9 cm. How do you calculate the size of the smallest angle in the triangle?

##### 1 Answer

Use the Law of Cosines (and a calculator) to determine:

smallest angle

#### Explanation:

Denote the sides as

and

Note that the smallest angle is the angle opposite the shortest side (i.e. angle

By The Law of Cosines:

or

Using the given values

If