Incenter of a right angle triangle trick

Finding incenter of a right angle triangle :-

Question: Finding incenter of triangle having side 3cm,4cm,5cm.

Sol:-

Incenter R= 2*area of triangle

                          sum of sides

Area of triangle = 1/2 (base * height)
                          = 1/2 *3*4
                          =6 cm2
sum of sides = a+b+c = 3+4+5= 12

R= 2*6
       12
   =  1 cm 

Trick:

           only applicable to right angle triangles:

incenter of right angle triangle R= 1/2(base+perpendicular-hypotenuse )

                                                     =1/2(3+4-5)

                                                     =1/2*2

                                                     = 1cm

Best Of Luck