Past exam of the mathematics course of the University of Cambridge / 2022 / iii / Paper 326 / 2 / c / ii / Solution

The graph is continuous and piecewise linear: it is horizontal at zero on $[-\lambda ,\lambda ]$ and has slope one outside that interval, joining the axis at $(-\lambda ,0)$ and $(\lambda ,0)$.

 psi
  ^
  |                    /
  |                   /
--+---------==========--------> x
 /         -lambda  lambda
/