Q. It is given that $\frac{1}{1^{4}} + \frac{1}{2^{4}} + \frac{1}{3^{4}} + ... + to\ \infty = \frac{\pi^{4}}{90}$. Then, $\frac{1}{1^{4}} + \frac{1}{3^{4}} + \frac{1}{5^{4}} + ...\infty$ is equal to

A) $\frac{\pi^{4}}{96}$
B) $\frac{\pi^{4}}{45}$
C) $\frac{89}{90}\pi$
D) None of these
Explanation

(a)
Since, $\frac{1}{1^{4}} + \frac{1}{2^{4}} + \frac{1}{3^{4}} + ...\infty = \frac{\pi^{4}}{90}$
$\Rightarrow \frac{\pi}{90} = \left( \frac{1}{1^{4}} + \frac{1}{3^{4}} + ...\infty \right) + \left( \frac{1}{2^{4}} + \frac{1}{4^{4}} + \frac{1}{6^{4}} + ...\infty \right)$
$\Rightarrow \frac{\pi^{4}}{90} = \left( \frac{1}{1^{4}} + \frac{1}{3^{4}} + ...\infty \right) + \frac{1}{2^{4}}\left( \frac{1}{1^{4}} + \frac{1}{2^{4}} + \frac{1}{3^{4}} + ...\infty \right)$
$\Rightarrow \frac{\pi^{4}}{90} = \left( \frac{1}{1^{4}} + \frac{1}{3^{4}} + ...\infty \right) + \frac{1}{16}\left( \frac{\pi^{4}}{90} \right)$
$\Rightarrow \frac{\pi^{4}}{96} = \frac{1}{1^{4}} + \frac{1}{3^{4}} + ...\infty$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.