Khan Academy Static

Sum_of_lengths_of_two_sides_of_a_triangle

The sum of the lengths of any two sides of a triangle is always greater than the third side. This is called Triangle Inequality Theorem.

Two_special_triangles_equilateral_and_isosceles

Here we will learn two special types of triangles: Equilateral and Isosceles. A triangle in which all the three sides are of equal lengths and the measure of each angle is 60 degree is called an 'equilateral' triangle , whereas a triangle with two sides equal is called 'Isosceles'. Also, the angles opposite to equal sides of an isosceles triangle are equal and on the basis of this property, we are going to find missing angles of triangles.

Angle_sum_property_of_a_triangle

The sum of the three interior angles of a triangle is always 180 degree. This property helps us solve a wide variety of problems based on Triangles.

Right_angled_triangles_and_Pythagoras_property

A right-angled triangle is the one in which the measure of one of the angles is 90 degrees. In a right-angled triangle, the square of the hypotenuse equals the sum of the squares of the other two sides. This is called Pythagorean Theorem. If the Pythagoras property holds, the triangle must be right-angled.