Hey i have this question given to me by teacher that i just cant wrap my head around i know the derivative of sin(x) is cos(x) but the way its done confuses me here's the question:

The self induced e.m.f (measured in volts, V) in an inductor can be found by using: e= L𝒅𝒊 𝒅𝒕 V, where L is the inductance in henrys. Calculate the induced e.m.f. when an inductor of 270mH passes a current: i = Bsin(314t+𝜋 6 ) ampere at the instant when time t = 10ms.(See table for your value of B)