यदि $$\int_\limits{0}^{\pi} \frac{5^{\cos x}\left(1+\cos x \cos 3 x+\cos ^{2} x+\cos ^{3} x \cos 3 x\right) \mathrm{d} x}{1+5^{\cos x}}=\frac{\mathrm{k} \pi}{16}$$ है, तो $$\mathrm{k}$$ बराबर है ____________ |