52. Tekislikda koordinatalari bilan berilgan a=(x1,y1) va b=(x2,y2) vektorlarning a·b skalyar ko‘paytmasini hisoblash formulasini ko‘rsating
a·b = x1 y1 + x2 y2
a·b = (x1+ y1)· (x2+ y2)
a·b = x1 y2 + x2 y1