1. diketahui titik P (3,5,0), Q (1,3,-1), R (-1,4,1). Hitunglah panjang vektor proyeksi PQ terhadap vektor PR 2.Diketahui A(1,2,-3), B(3,5,2) dan vektor p=2i+2j

1./ P = (3, 5, 0)
Q = (1, 3, -1)
R = (-1, 4, 1)

PQ = Q - P
= (1, 3, -1) - (3, 5, 0)
= (-2, -2, -1)

PR = R - P
= (-1, 4, 1) - (3, 5, 0)
= (-4, -1, 1)

proyeksi PQ terhadap PR
= PQ × PR / |PR|^2 × PR
= (-2, -2, -1) × (-4, -1, 1) / (_/(-4)^2 + (-1)^2 + (1)^2)^2 × (-4, -1, 1)

= (8, 2, -1) / 18 × (-4)
= 9/18 × (-4)
= 1/2 × (-4) = -2

Bisa jg dijadikan
(8 × (-4))i /18 + (2 × (-4))j /18 + (-1 × (-4))z /18
= -16/9 i + (-4)/9 j + 2/9 z

atau
(-16/9, -4/9, 2/9)

yg no. dua dicoba sendiri yah.. jawabannya buanyak soalnya.. tp caranya mirip no. 1.. semoga membantu