Draw any triangle. In this case, name the vertices of the triangle as A, B, and C.
From the figure, the measurement of ∠B or ∠ABC is 90°. On the other hand, since sides AB and AC are of equal lengths, the triangle is an isosceles triangle. Thus, ∠A or ∠CAB and ∠C or ∠ACB both measure 45°.
The measurements of the angles can be obtained using a protractor, or in this case, since the triangle is an isosceles triange, the base angles are equal.
Since the sum of the interior angles of a triangle is 180°, and one of the angles already measures 90°, the other two angles must share equally the remaining 90°.
