Rearranging an electronics eqn: i = 12Sin(31.4t)

[hdnixon]

I am studying electronics and this question has cropped up on an assignment i have...

It is to do with sinusoidal waveforms and a.c circuits (and needs to be calculated in Radians on a calculator)

i = 12Sin(31.4t) or Current = 12 x Sin(31.4 x Time)

The formula calculates the current in a 5Hz a.c signal (Frequency = 31.4/2pi = 5Hz ) dependant on time and if plotted on a graph looks like this:

The question i'm struggling with is this:
Determine the time taken for the current to reach 10Amps for the first and second time. ( Find t when i=10 )

This needs to be done by rearranging the formula but i cant manage it. From the graph i know the answer is about 0.031 and 0.069

Ive tried every possible way of rearranging the formula but the fact that Time is in the brackets and the added complexity of the Sine has made all my efforts so far useless

Hope somebody can help

 

[stapel]

i = 12Sin(31.4t) or Current = 12 x Sin(31.4 x Time)

Determine the time taken for the current to reach 10Amps for the first and second time. ( Find t when i=10 )

Plug "10" in for "i", divide through by 12, and take the inverse sine. Then divide through by 31.4.

Of course, you'll have to use your knowledge of sines to get the other solution(s).

Eliz.