Question

determining unknowns 1. an isosceles triangle has base angles that measure 58°. write an equation to determine the measure of the third angle.

Explanation:

Step1: Recall triangle angle sum rule

The sum of angles in a triangle is $180^\circ$.

Step2: Define variable for unknown angle

Let $x$ = measure of third angle.

Step3: Set up the equation

The two base angles are each $58^\circ$, so:
$58 + 58 + x = 180$
Or simplified:
$116 + x = 180$

Answer:

$58 + 58 + x = 180$ (or $116 + x = 180$)