Post History

You're going to need to differentiate the curves where they pass through the origin, and also find the angle of the intercept.

$$\frac{\textrm{d}}{\textrm{d}x} \textrm{blue curve}\Big\vert_{x=0} = 0$$ giving a limit $\theta_0=0$.

$$\frac{\textrm{d}}{\textrm{d}x} \textrm{red curve}\Big\vert_{x=0} = 3$$ giving a limit $\theta_2=\arctan 3$.

The intersection is at $x=2, y=2$, giving a cutoff at $\theta_1 = \arctan \tfrac22$.