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Question

Mathematics Question on Vector Algebra

Find the angle between two vectors a\vec{a} and b\vec{b} with magnitudes 3\sqrt3 and 22, respectively having a.b=6.\vec{a}.\vec{b}=\sqrt{6}.

Answer

The correct answer is:π4\frac{π}{4}
It is given that,
a=3,b=2|\vec{a}|=\sqrt{3},|\vec{b}|=2 and a.b=6\vec{a}.\vec{b}=\sqrt{6}
Now,we know that a.b=abcosθ.\vec{a}.\vec{b}=|\vec{a}||\vec{b}|cosθ.
6=3×2×cosθ∴\sqrt{6}=\sqrt3\times2\times cosθ
cosθ=12⇒cosθ=\frac{1}{\sqrt2}
θ=π4⇒θ=\frac{π}{4}
Hence,the angle between the given vectors a\vec{a} and b\vec{b} is π4\frac{π}{4}.