A(0, 0)
C(a, a)
The formula of a midpoint of AC:
[tex]\left(\dfrac{x_A+x_C}{2},\ \dfrac{y_A+y_C}{2}\right)[/tex]
Substitute:
[tex]x=\dfrac{0+a}{2}=\dfrac{a}{2}\\\\y=\dfrac{0+a}{2}=\dfrac{a}{2}[/tex]
Answer: [tex]\left(\dfrac{a}{2},\ \dfrac{a}{2}\right)[/tex]
