your notation leaves something to be desired.
always write down the units. what you do with the values, do with the units
if the resulting units are incorrect, you made a mistake somewhere
you did not multiply the power, 3 for phases, voltage and power factor
you divided them:
power per phase = 25000 W / 3 = 8333.33 W
phase current = 8333.33 W / 415 V / 0.8 = 25.1 A
as for the angle, cos^-1 (0.8) = 36.87 degrees or arccos(0.8) = 36.87 degrees
use divide (/) for divide, and multiply (x) for multiply and ^ for exponents
as for the phasor diagram, the phase voltage is 415V at 0 degrees
you calculated the phase current at 25.1 A at 36.87 degrees
you calculated the stator drop as 100.4 V at 126.87 degrees
they are phasors, not vectors, but is you draw them like vectors,
you should be through b i, and need only connect E between the appropriate phasors to get ii
for iii, either measure or calculate E - like i said, they are phasors, not vectors, but the calculation is the same
likewise for iv