Radius from Blackbody Radiation (2)

Blackbody radiation law says that the energy emitted / area / time by the star is determined only by its TEMPERATURE
So if we can determine the LUMINOSITY (energy emitted / time) of the Star, we can combine this with its TEMPERATURE to determine the RADIUS
TEMPERATURE + LUMINOSITY + BLACKBODY RADIATION => RADIUS

Blackbody radiation law says that the energy emitted / area / time by the star is determined only by its TEMPERATURE