The length of perpendicular from foci $S,S'$,on any tangent to ellipse $$\frac{x^2}{4}+\frac{y^2}{9}=1$$ are $a,c$ respectively then value of $\int \{x\}dx$ from $-ac$ to $ac$ is ?(where {} denotes the fractional part.).
My attempt. Now this is a standing ellipse so I assumed a tangent at $(4,0)$ as we know the distance between tangent and focus is $4$. And by symmetry we can say $a=c$ so $-ac=16,ac=16$ now I am not getting what is that $n$ and how to compute the integral. Thanks