Answer
$E=\sqrt {12.5} \sin \theta+\sqrt {12.5} \cos \theta$
Work Step by Step
We have: $\tan \dfrac{\pi}{4}=1$
When $a=b$; $\sqrt {a^2+b^2} = 5$
$ \implies 5=\sqrt {2a^2}$
or, $a=b=\sqrt {12.5} $
Now, $E=\sqrt {12.5} \sin \theta+\sqrt {12.5} \cos \theta$
