for beginners
➔ D o m e i nwith one square root
➔ D o m e i nwith two square roots
➔ D o m e i nwith sin, cos, tan, ...
➔ D o m e i nconditional functions
➔ D o m e i nwith logarithm of e
➔ B e r e i k (Range)the simplest
➔ B e r e i k (Range)most difficult