Because sine is opposite side/ hypotenuse. tangent = opposite angle / adjacent, so we need to find the adjacent side using Pitagora's theorem
[tex]\begin{gathered} c^2=a^2+b^2 \\ 41^2=9^2+b^2 \\ 1681\text{ - }81=b^2 \\ \sqrt{1600}=b \\ 40=b \end{gathered}[/tex]And now we find tangent.
[tex]tan\theta=\frac{oppositeside}{adjacentside}=\frac{9}{40}[/tex]So, the correct option is C