Сделаем построение
AB = DC = a
AD = BC = b
AO = 1/2*AC = 1/2*(AB + BC) = 1/2*(a + b) = (a + b)/2
AK = AB + BK = a + b/2
KD = KA + AD = -AK + AD = -(a + b/2) + b = -a - b/2 + b = -a+b/2
Сделаем построение
AB = DC = a
AD = BC = b
AO = 1/2*AC = 1/2*(AB + BC) = 1/2*(a + b) = (a + b)/2
AK = AB + BK = a + b/2
KD = KA + AD = -AK + AD = -(a + b/2) + b = -a - b/2 + b = -a+b/2