We can derive a triangle called the impedance triangle from the phasor diagram of an RL series circuit as shown.
The impedance triangle is right angled triangle with R and XL as two sides and impedance as the hypotenuse. The angle between the base and hypotenuse is Φ. The impedance triangle enables us to calculate the following things.
1. Impedance \(Z=\sqrt{R^2+X^2_{L}}\)
2. Power Factor \(cos\theta=R/Z\)
3. Phase angle \(\theta=tan^{-1}(\frac{X_{L}}{R})\)
4. Whether current is leading or lagging
