Mark the correct alternative in each of the following:

If θ is an acute angle and the vector is perpendicular to the vector then θ =

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If are two unit vectors inclined at an angle θ such that then

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Let be three unit vectors such that is perpendicular to . If makes angle α and β respectively, then cos α + cosβ =

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The orthogonal projection of is

Mark the correct alternative in each of the following:

If be two unit vectors and θ is the angle between them. Then is a unit vector, if θ =