Exercise 2 Page 211

We have been given the measures of the two angles of a triangle, 72 and 72. We will find the measure of the third angle using the Triangle Angle-Sum Theorem. This theorem tells us that the measures of the interior angles of a triangle must add to 180^(∘).

If we let x be the unknown measure of the third angle, we can create an equation to solve for the third angle.

72+ 72+ x=180

AddTerms

Add terms

144+x=180

SubEqn

LHS-144=RHS-144

x=36

The measure of the third angle is 36^(∘).