[tex]Zadanie\\\\S=(\frac{x_A+x_B}{2}\ ;\ \frac{y_A+y_B}{2})\\\\S=(\frac{1+8}{2}\ ;\ \frac{2+4}{4})\\\\S=(\frac{9}{2}\ ;\ \frac{6}{2})\\\\S=(4,5\ ;\ 3)[/tex]
