In a right triangle, one of the angle is of 90 degrees. The sum of other two angles will be 90 degrees. Two special right triangles are 45-45-90 and 30-60-90. 45-45-90 triangle is formed by cutting the square in half along with the diagonal. This triangle is also called isosceles right triangle as two sides are equal. 30-60-90 triangle is formed by cutting equilateral triangle in half.
The specaility of these two triangles are that length of the sides of the triangle are in a certain fixed ratio. The ratio can be found out by using pythagoras theorem.
The Pythagorean Theorem is a mathematical relationship between the sides of a right triangle. A right triangle is any triangle that has one right internal angle. According to this theorem, if the length of the legs (smallest sides) are squared and their sum is found, the sum will be equal to the square of the hypotenuse (longest side).