Indefinite Integration

$\frac{1}{3} \log \left|\frac{\sin x}{\sin x+3 \cos x}\right|+C$

$\log \left|\frac{\cos x}{\sin x+3 \cos x}\right|+c$

$\frac{1}{3} \log \left|\frac{\cos x}{\sin x+3 \cos x}\right|+C$

$\log \left|\frac{\sin x}{\sin x+3 \cos x}\right|+c$