Q23 of 138 Page 24

Mark the correct alternative in each of the following:

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


We know that,


(i)


Since,


is perpendicular to


=0


And according to question


=1


We can rewrite equation (i) as



1=1+1+1+0+2(cos α + cosβ)


cos α + cosβ = -1 Ans.

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