When current is leading or lagging voltage, the value of that integral will always be less than the value for the in-phase case over the same interval. This reflects the attribute of an inductor or a capacitor to act as energy stores. At various points through the AC cycle, the reactive component is either storing energy or returning it to the system. Perfectly sinusoidal waveforms follow Pythagoras, where the square of the apparent power is equal to the squares of the active power and reactive power is measured in reactive volt amperes. The relationship is conventionally visualized in a right-angled triangle vector diagram. Perfectly sinusoidal waveforms follow Pythagoras, where the square of the apparent power is equal to the squares of the active power and reactive power measured in reactive volt amperes (var).