Hard calculation

Hi and thanks a lot for your wonderfull plugin!

I need to set a calculation for fabric veils.
User has to input 3 lenghts if its a triangular veil
Or 4 lenghts if it’s a square veil.
We need to calculate the surfaces (m2).

Formula for triangle is quite complicated :
https://www.lememento.fr/aire-triangle-sans-hauteur

Do you have a form already made for that?
Regards