Let's find the inflection points, we'll need to solve the equation for this
$$\frac{d^{2}}{d y^{2}} f{\left(y \right)} = 0$$
(the second derivative equals zero),
the roots of this equation will be the inflection points for the specified function graph:
$$\frac{d^{2}}{d y^{2}} f{\left(y \right)} = $$
the second derivative$$\left(4.5 \cdot 10^{-6} \left(\cot^{2}{\left(y \right)} + 1\right) \delta\left(\frac{0.003 \cot{\left(y \right)} + 1}{2}\right) + 0.003 \cot{\left(y \right)} \operatorname{sign}{\left(0.003 \cot{\left(y \right)} + 1 \right)}\right) \left(\cot^{2}{\left(y \right)} + 1\right) = 0$$
Solve this equationThe roots of this equation
$$y_{1} = 1.5707963267949$$
Сonvexity and concavity intervals:Let’s find the intervals where the function is convex or concave, for this look at the behaviour of the function at the inflection points:
Concave at the intervals
$$\left(-\infty, 1.5707963267949\right]$$
Convex at the intervals
$$\left[1.5707963267949, \infty\right)$$