Abstract
Heisenberg and Robertson-Schrodinger uncertainty relations for the coordinate and momentum follow from two stronger uncertainty relations. The first uncertainty relation has classical character and its right-hand side can have an arbitrary value greater than or equal to zero.
The second uncertainty relation has quantum character and its right-hand side equals ħ2/4; its existence is related to the existence of the envelop of the wave function. These two uncertainty relations cannot be obviously improved on.
The equality sign in the second relation can be achieved for much larger class of the wave functions than in case of the Heisenberg or Robertson-Schrodinger uncertainty relations.