Exercise 9 Page 115

The sum of the measures of the interior angles of a triangle is 180^(∘).

30^(∘), 60^(∘), and 90^(∘)

Practice makes perfect

We want to find the measures of the angles in the given triangle.

To find these angle measures, we will first recall a key piece of information!

Angle Sum of a Triangle
The sum of the measures of the interior angles of a triangle is 180^(∘).

With this rule, we can write an equation connecting the measures of the angles of our triangle. Recall that the measure of a right angle is 90^(∘). x^(∘)+ 30^(∘)+ 90^(∘)=180^(∘) Let's solve the equation and find the value of x. For simplicity, we will not write the degree symbol.

x+30+90=180

AddTerms

Add terms

x+120=180

SubEqn

LHS-120=RHS-120

x=60

The measure of the angle is 60^(∘).