→ →
AB = DC , D = ( x, y)
[ 7, − 1] = [ 9 − x, 4 − y]
7 = 9 − x i − 1 = 4 − y
x = 2 i y = 5
D = ( 2, 5)
=======
Oblicz: I AC I i I BD I
Pole
P = 0, 5*( AC I * I BD I =
BA→=[−7,1]
C=(9,4)→T[−7,1]⇒D=(9−7,4+1)=(2,5)
| |AC|*|BD| | ||
PABCD= | ||
| 2 |