If θ is the angle between two vectors veca and vecb, then veca . vecb = 0 only when ______.

Question

If θ is the angle between two vectors veca and vecb, then veca . vecb >= 0 only when ______.

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If $\theta$ is the angle between two vectors veca and vecb, then veca . vecb >= 0 only when underline(0 $\leq$ $\theta$ $\leq$ pi/2). Explanation: Let $\theta$ be the angle between two vectors, veca and vecb. Then, without loss of generality, veca,vecb are non zero vectors so that |veca|,|vecb| are positive It is known that `veca $\times$ vecb = |veca||vecb|cos$\theta$ a $\times$ b $\geq$ 0 |veca||vecb|cos$\theta$$\geq$0 cos$\theta$ $\geq$ 0 0 $\leq$ $\theta$ $\leq$ ($\pi$/2) So, a $\times$ b $\geq$ 0 when 0 $\leq$ $\theta$ $\leq$ ($\pi$/2).`

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