How to represent a triangle from a TS diagram in PV diagram

Question

Answer 1

1. Isothermal process:

Note that constant temperature line is drawn such that entropy has decreased. Why? Why not along increasing entropy? Keep this funda in mind that increase/decrease in entropy in T-s diagram is determined only by a single phenomenon : Heat addition/rejection.

If heat is being added, entropy will increase. If heat is being rejected, entropy will decrease. 1 – 2 is compression still temperature is same. Using first law, this is possible only if the system is rejecting heat, so entropy should also decrease.

Comments

So the base of the triangle represents an isothermal process which can be represented by a slightly curved line in PV diagram.
Moving on, the perpendicular represents an isentropic process, implying an adiabatic process which is also represented by a curved line but with a steeper slope than an isotherm.
But what about the the hypotenuse? How do you represent it in PV diagram?