Question: The value of
$\cos ^{3}\left(\frac{\pi}{8}\right) \cdot \cos \left(\frac{3 \pi}{8}\right)+\sin ^{3}\left(\frac{\pi}{8}\right) \cdot \sin \left(\frac{3 \pi}{8}\right)$
is:
$\frac{1}{4}$
$\frac{1}{\sqrt{2}}$
$\frac{1}{2 \sqrt{2}}$
$\frac{1}{2}$
Correct Option: , 3
Solution:
