Answer
($\frac{a}{2}$,$\frac{b}{2}$)
Work Step by Step
Given
Points(a,0) and (0,b)
if x1=a,y1=0,x2=0,y2=b
Mid point of these two points is($\frac{x1+x2}{2}$,$\frac{y1+y2}{2}$)
($\frac{a+0}{2}$,$\frac{0+b}{2}$)
= ($\frac{a}{2}$,$\frac{b}{2}$)