I am reading a book on principles and applications, the is a list of questions for you to answer. so far i have been doing ok with. but one has me a little stuck on getting to the correct answer. some how i managed to find some of the answer and some of my thinking was right. but i cant get the exact answer. i have looked at the answer at the end of the chapter and worked my way around it but was hoping for there to be a way that i could understand. i have tried rearranging the formula to get the right answre.

here is the question

dteremine the frequency and periodic time for an alternating emf having an instantaneous voltage of 5v, 0.02 seconds after passing through zero if the peak value is 12v.

there are examples in the book that i looked at that gave me some idea. i wrote out the formula like this

5v = 12v sin(2pi * ? * 0.02), i tried to rearrange this and got 3.324 which is close to the answer. divide everything by 5 except what i dont have, the frequency.

then i looked at an example

5/12 = 0.416, this inverse sin 0.416 = 0.42977 (rad) which is getting somewhere closer i think. convert this to degrees to get 24.62, put this in 12vsin(24.62) = 4.99volts. so 0.42977 has something to do with the answer. after mucking around i got 0.42977/ 2pi * 0.02 = 3.42 Hz which is close and 1 / 3.42 = 0.29

I dont know if there is a better way than to look at the answer and muck about with it. i dont feel like i have understood the question or how to do it.....because i havent and i cant.

please please help

thanks

simon