1.

FInd the angle between the vectors i + 2j + 3k and 3i -j+2k.

Answer»

a=i+2j+3k

b=3i-j+2k

we know thati.i=1 , j.j=1 , k.k=1.andi.j=j.i=i.k=k.i=j.k=k.j=0.

a.b=3-2+6=7

a.b=abcosθ

cosθ=(a.b)÷ab

{a=√a.a, b=√b.b} [a=√14=b}

cosθ=7÷(14)=.5

θ=60



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