Using Pythagoras Theorem, the third side of a right-angled triangle can be
calculated when two sides are given.
Suppose A = length of
hypotenuse and
B & C = lengths of the sides containing the
right angle
Then (A^2) = (B^2)+(C^2)
Proof:
If a = angle opposite side A ( =90 degrees)
b = angle opposite side B
c = angle opposite side C
then B = A sin a and C = A cos a
Squaring and adding,we get the result.