a, \(tan\left(3x+1\right)=1\)
\(\Leftrightarrow tan\left(3x+1\right)=tan\dfrac{\pi}{4}\)
\(\Leftrightarrow3x+1=\dfrac{\pi}{4}+k\pi\)
\(\Leftrightarrow x=\dfrac{\pi}{12}-\dfrac{1}{3}+\dfrac{k\pi}{3}\)
b, \(cot3x=\sqrt{3}\)
\(\Leftrightarrow cot3x=cot\dfrac{\pi}{6}\)
\(\Leftrightarrow3x=\dfrac{\pi}{6}+k\pi\)
\(\Leftrightarrow x=\dfrac{\pi}{18}+\dfrac{k\pi}{3}\)