Formula and interpretation
A mathematical formula is useful only when its assumptions, symbols, variable units and domain are understood. For example, the magnitude of z=x+iy is |z|=√(x²+y²), while its argument needs a quadrant-aware atan2(y,x) rather than simply arctan(y/x).
Worked complex magnitude example
For z = 3 + 4i, the magnitude is √(3²+4²)=5. Its principal argument is atan2(4,3)≈53.13° (approximately 0.9273 rad). This basic identity helps check alternating-current phasors, complex roots and vector representations.