Odpowiedź:
C = (- 6 , 7 ) , D = ( 2 , 11 ) , E = (xe , ye)
xc = - 6 , xd = 2 , yc = 7 , yd = 11
xd = (xc + xe)/2
2 * xd = xc + xe
xe = 2 * xd - xc = 2 * 2 + 6 = 4 + 6= 10
yd = (yc + ye)/2
2 * yd = yc + ye
ye = 2 * yd - yc = 2 * 11 - 7 = 22 - 7 = 15
E = ( 10 , 15 )