Diketahui : a= i+2j+ Pk dan b:-3i+4j-5k .dika a dan b

a = i + 2j + Pk –> a = (1, 2, P)

b = -3i + 4j – 5k –> b = (-3, 4, -5)

a dan b saling ortogonal, maka a . b = 0

a . b = 0

(1, 2, P) . (-3, 4, -5) = 0

(1)(-3) + (2)(4) + P(-5) = 0

-3 + 8 – 5P = 0

5 – 5P = 0

5 = 5P

1 = P

P = 1