1. Show that in a right angled triangle, the hypotenuse is the longest side.
Consider a right-angled triangle ABC with right angle at A.
We know that the sum of interior angles of a triangle is 180.
So,
or
or
Hence and are less than ().
Also, the side opposite to the largest angle is also the largest.
Hence the side BC is largest is the hypotenuse of the .
Hence it is proved that in a right-angled triangle, the hypotenuse is the longest side.