diketahui segitiga abc dengan titik a(2,-1,-3), b(-1,1,-11),dan c(4,-3,-2).proyeksi vektor ab pada ac=

a(2,-1,-3), b(-1,1,-11),dan c(4,-3,-2).

ab = b - a = (-1, 1, -11) - (2, -1, -3) = (-3, 2, -8)
ac = c - a = (4, -3, -2) - (2, -1, -3) = (2, -2, 1)

ab . ac = (-3, 2, -8) × (2, -2, 1) = (-6 - 4 - 8) = (-18)

|ac| = √(2)² + (-2)² + (1)² = √9 = 3

Proyeksi vektor ab pada ac

|d| = ab × ac / |AC|
|d| = -18 / 3
|d| = -6