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If $vec{a}$ and $vec{b}$ are non-zero vectors making an angle $theta$, then $vec{a} \cdot vec{b}$ is equal to
A$|\vec{a}||\vec{b}|\sin\theta$
B$|\vec{a}||\vec{b}|\cos\theta$
C$\dfrac{|\vec{a}|}{|\vec{b}|}\cos\theta$
D$|\vec{a}|^2+|\vec{b}|^2$
Answer & Solution
Correct answer: B. $|\vec{a}||\vec{b}|\cos\theta$
The scalar product of two vectors is defined by $\vec{a}\cdot\vec{b}=|\vec{a}||\vec{b}|\cos\theta$, where $\theta$ is the angle between them. Hence option B is correct.
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