The third side can be calculated using pythagoras theorem The side facing the right-angled (90∘) is the hypotenuse (c). From the question hypotenuse =13 Let x= the third side x2+52=132 x2+25=169 x2=169−25 x2=144 A number when multiplied by itself gives 144.12×12 is 144 , hence express 144 as 12×12 or 122 x2=122 Since the powers are the same, the bases are also the same. x=12 The third side =12