• Mar 6th 2010, 09:59 PM
flowergirl5
was not quite sure how 2 solve sin((Pi*x)/3)=0 and while looking at the answer it gave 3j and j where r the j's from

regards Flowergirl5
• Mar 6th 2010, 10:30 PM
Prove It
Quote:

Originally Posted by flowergirl5
was not quite sure how 2 solve sin((Pi*x)/3)=0 and while looking at the answer it gave 3j and j where r the j's from

regards Flowergirl5

$\displaystyle \sin{\frac{\pi x}{3}} = 0$

$\displaystyle \frac{\pi x}{3} = \arcsin{0}$

$\displaystyle \frac{\pi x}{3} = \pi n$, where $\displaystyle n$ is an integer representing the number of times you have gone around the unit circle...

$\displaystyle \pi x = 3\pi n$

$\displaystyle x = 3n$.

In this case, they have just used $\displaystyle j$ where I have used $\displaystyle n$.
• Mar 7th 2010, 02:36 AM
HallsofIvy
Actually n, or j, is the number of times you have gone halfway around the unit circle. sine is 0 at any multiple of $\displaystyle \pi$.

(Until I saw Prove It's answer I was about to try to make "j" the imaginary unit!)