A) \[2\text{ }r\text{ }sin(\theta /2)\]
B) \[2\text{ }r\text{ cos}(\theta /2)\]
C) \[2\text{ }r\text{ tan}(\theta /2)\]
D) \[2\text{ }r\text{ cot}(\theta /2)\]
Correct Answer: A
Solution :
\[\Delta \overrightarrow{r}={{\overrightarrow{r}}_{2}}-{{\overrightarrow{r}}_{1}};\] where\[{{r}_{2}}={{r}_{1}}=r\] Hence, \[\Delta r=\sqrt{r_{2}^{2}+r_{1}^{2}-2{{r}_{2}}{{r}_{1}}\cos \theta }=2r\sin \frac{\theta }{2}\]You need to login to perform this action.
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