Question

If $\theta$ is the angle between two vectors $\overrightarrow{a}$ and $\overrightarrow{b}$ , then $\overrightarrow{a}.\overrightarrow{b}>0$ only if

• A. $0\le \theta \le \pi$
• B. $\frac{\pi }{2}\le \theta \le \pi$
• C. $0\le \theta \le \frac{\pi }{2}$
• D. $0<\theta <\frac{\pi }{2}$

Answer 1

Answer: (D)

$\vec{d}.\vec{b}=abcos\theta >0$ if $0<0<\frac{\pi }{2}\left[\because cos\theta >0\right]$