A sinusoidal current wave has an instantaneous value of -20 A at t = 0 and is increasing negatively. If the peak value is 50 A, solve for the instantaneous value of the current when t = 3 milliseconds...

A sinusoidal current wave has an instantaneous value of -20 A at t = 0 and is increasing negatively. If the peak value is 50 A, solve for the instantaneous value of the current when t = 3 milliseconds and at t = 40 milliseconds. At what time will the instantaneous value of the current be -30 A for the 4th time.