The general form for a limacon is #r=a+bcostheta# or #r=a+bsintheta#. When will a limacon have a dimple?
Please see below.
Observe that we can write
Hence, there is not much of a difference and either can represent a limacon. However, general form used is
If the equation is
Limacon will have a dimple if
Additional Information - Limacon will have inner loop if