How can i calculate arc/radius in soft entrence milling?

Hello!

Sorry for bad english, and sorry if i post this wrong! but i want to know how you guys program manuell soft entrence when milling,
what decides what radius you going to have?

I did a quick example. i just want to know how i can learn to calculate kind of that stuffs, make a radius in to the end point.

how you guys think and doing it when you are programming ?

when our programmer at work are making programs manuell sometimes hes very quick and make soft entrance and kind of that stuffs, but he
has left our job know to another so i cant ask him..

I hope someone understand my bad english and can help me be a better programmer =)

best regards