: A triangle which has three right angles is called a right angled triangle. The sum of any two angles of a right-angled triangle is always greater than 900. The arms of a right-angled triangle can be equal or unequal. When drawing perpendiculars from opposite vertices of a right-angled triangle to opposite sides , the intersection of the perpendiculars is always located inside the triangle. The center of gravity , the center, the center , and the perpendicular center of a right -angled triangle are all located inside the triangle.