If the projection of 2 i ^ + 4 j ^ - 2 k ^ on i ^ + 2 j ^ + α k ^ is zero. Then, the value of α will be

Question

If the projection of 2 i ^ + 4 j ^ - 2 k ^ on i ^ + 2 j ^ + α k ^ is zero. Then, the value of α will be,

MARKS App · Accepted Answer

Given here: a → = 2 i ^ + 4 j ^ - 2 k ^ and b → = i ^ + 2 j ^ + α k ^ Now, a → · b → = 0 , as a → should be perpendicular to b → . ∴ 2 × 1 + 4 × 2 - 2 × α = 0 ∴ α = 5

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