A 50 cycle ac has a maximum instantaneous value of 42.42A.It crosses the zero axis in a positive direction when time is zero. Determine a)time when current first reaches a value 30a
b) time when current after a ahving gone through its maximum positive values reaches a value of 36.7 amp
c)value of the current when the time is 1/20 sec
d) value when current first reaches a negative value of 21.21amp.