In the following figure, find and .
Step 1: Find .
Since and are congruent,
is an isosceles triangle. In any isosceles
triangle, the angles opposite to the congruent sides are
Since and are parallel lines
crossed by transversal , and are alternate interior angles with
the same angle measure.
Step 2: Find .
Write an equation to show that sum of angle measures in is .
Let represent and solve for .