This is a sine wave of magnitude 1.5. The value offor any value ofiis found by straight-forward sunstitution intoteh formula you gave us. Thus at t = 20 milliseconds you have:t

However, you didn't tell us whether this formula yieldsin amps, or milliamps. Presumbaly you can convert if need be.i

The second queston involves finding the inverse of the sine function. Your post is missing an important part of the question - namely precisely what value ofyou were given. So I will give an example wherei= 0.75. You have:i

For what value of does ? From basic triginometry you know that and . Hence:

or

Hope this helps.