Thank you for reporting, we will resolve it shortly
Q.
A current $i$ is flowing in a straight conductor of length $L$. The magnetic induction at a point on its axis at a distance $\frac{L}{4}$ from its centre will be:
$|\overrightarrow{ B }|$ at point $P$ is:
$
B =\frac{\mu_{0} i }{4 \pi R }\left(\sin \theta_{1}+\sin \theta_{2}\right)
$
here $R =\frac{ L }{4}$
$\sin \theta_{1}=\sin \theta_{2}=\frac{\frac{L}{2}}{\sqrt{\left(\frac{L}{2}\right)^{2}+\left(\frac{L}{4}\right)^{2}}}=\frac{4}{2 \sqrt{5}}$
$
\text { so } B =\frac{\mu_{0} i }{4 \pi \frac{ L }{4}}\left(\frac{4}{2 \sqrt{5}}+\frac{4}{2 \sqrt{5}}\right)
$
$\Rightarrow B=\frac{4 \mu_{0} i}{\sqrt{5} \pi L}$