# Find the angle between two vectors. A = i + 2j – u and B = -4i + j - 2u.

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Find the angle between two vectors. A = i + 2j – u and B = -4i + j - 2u.

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AB = | A | | B | cos θ

∴ cos θ = $\frac{A.B}{|A||B|}$

A.B= ( i+ 2j –u ).(−4i +j - 2u)

⇒ (−4 + 2 + 2) = −4 + 4 = 0

cos θ = 0

θ = cos-1 0

Hence, θ = 90º.