A set that is not convex is called a non-convex set. A polygon that is not a convex polygon is sometimes called a concave polygon, and some sources more generally use the term concave set to mean a non-convex set, but most authorities prohibit this usage.
In either case you don't need to deal with the absolute value. A rectified sine wave is a periodic signal with a period equal to half of the full sinusoid, I would write the sine in exponential form and integrate over one period to find the series coefficients.
A rectifier is diode circuit designed to get dc out put from an ac input. There is full wave and half wave rectifiers. Full wave rectifiers are bridge rectifiers and half wave rectifiers are single diode rectifiers.It is used in power supplies of electronic systems.he term rectifier is sometimes applied to other devices but specifically a rectifier is a combination of diodes used to convert AC voltage to DC voltage. The rectifier is either half-wave or full-wave.