state and prove bernoulis theorem?

bernoulis theorem states that total energy of steady or terbulant flow is always contsant.... that is (pressure energy + kinetic energy + potential energy= constant) here anew kind of energy that is pressure energy is always present in fluid (you may have learnt in gas laws PV=nRT here PV is the pressure energy) hence we can say that for a steady flow.. PV+1/2mv^2+mgh=constant.... dividing both sides by V what do we get is the bernuolis theorem...