Step 1: Find .
For any two right-angled triangles, the triangles are congruent if the legs of one triangle are congruent to the legs of the other triangle.
In right-angled triangles and , and are congruent to each other, and and are congruent to each other.
Therefore, and are congruent to each other.
Since the triangles are congruent, .
Step 2: Find .
Write an equation to show that , , and are complementary (with a sum of ). Let represent , and solve for .
Step 3: Find .
Since and are congruent, is an isosceles triangle. In any isosceles triangle, the angles opposite to the congruent sides are congruent.
Write an equation to show that the sum of 's angle measures is . Let represent and . Solve for .