The current ' i ' in an inductance coil varies with time ' t '...

(1) For time interval $0 < t < T / 2$ $I=k t$, where $k$ is the slope For inductor as we know, induced voltage (V=-L \frac{d i}{d t}) (\Rightarrow V_1=-K L) (2) For time interval (\frac{T}{2} < t < T) (I=-K t \Rightarrow V_2=K L)