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Question
Find the value λ for which the vectors `vec"a"` and `vec"b"` are perpendicular, where `vec"a" = 2hat"i" + 4hat"j" - hat"k"` and `vec"b" = 3hat"i" - 2hat"j" + lambdahat"k"`
Solution
When `vec"a"` and `vec"b"` are ⊥r then `vec"a"*vec"b"` = 0
`vec"a"` ⊥r `vec"b"` ⇒ `vec"a" * vec"b"` = 0
(2)(3) + (4)(– 2) + (– 1)(λ) = 0
6 – 8 – λ = 0
– λ – 2 = 0
⇒ – λ = 2
⇒ λ = – 2
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