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.