Exercise 10 Page 612

From the diagram, we see that the triangle is equilateral. According to the Corollary to the Base Angles Theorem, if a triangle is equilateral, then it is equiangular.

According to the Triangle Sum Theorem, the sum of the measures of the interior angles of a triangle is

18 0^{\circ} .

Therefore, we can write the following equation.

3 x^{\circ} + 3 x^{\circ} + 3 x^{\circ} = 18 0^{\circ}

Let's solve this equation.

3 x^{\circ} + 3 x^{\circ} + 3 x^{\circ} = 18 0^{\circ}

AddTerms

Add terms

9 x^{\circ} = 18 0^{\circ}

DivEqn

$LHS / 9 = RHS / 9$

x^{\circ} = 2 0^{\circ}