A triangle is given by $A=(0,0), B=(5,1)$ and $C=(2,4)$. I already know $\lambda^2(\Delta ABC)=9$. Now I want to compute the area by using Cavalieri's principle.
I know how to start when I have to use the principle for volumes, but I don't know how to start here. I thought about intercept theorem, but then I don't know how to find the ratios.
Any hints are appreciated.