In elementary geometry, angles are always considered to be positive and not larger than 360∘. You also learned that the sum of the angles in a triangle equals 180◦, and that an isoscele...In elementary geometry, angles are always considered to be positive and not larger than 360∘. You also learned that the sum of the angles in a triangle equals 180◦, and that an isosceles triangle is a triangle with two sides of equal length. Recall that in a right triangle one of the angles is a right angle. Thus, in a right triangle one of the angles is 90◦ and the other two angles are acute angles whose sum is 90◦ (i.e. the other two angles are complementary angles).