Triangles are those closed convex polygons having three sides. We have already familiar with the different types of triangles. Right angled triangle is the one in which one of the interior angle of a triangle is a right angle. The longest side of the right triangle is called its Hypotenuse and the other two sides including the right angle are called as its legs or the base and the perpendicular. It is very much necessary to learn more about the right angled triangle, as it is very much helpful to find the height of a building, distance between the two buildings, vertical height of an aeroplane at a given instant etc. In this section let us discuss about the different formulae we use for a given right angled triangle.