# Am I or the book wrong?

• Mar 30th 2013, 10:42 PM
Paze
Am I or the book wrong?
I solved this. All except the +/- thing?

I get 0.007+/-n*2*pi or 3.13+/-n*2*pi.

The book claims: 0.41+n*2*pi or 2.73+n*2*pi.

First of all I don't understand why we are getting different values. Second of all I don't understand why the book does only plus and not plus/minus. I do admit I am a little uncomfortable with trig equations and my error could be silly but I hope you can help me out.

EDIT: Whoops...I noticed in my calculation that I was using the radians to calculate to radians.. arcsin0.4 - Wolfram|Alpha

The arcsin of 0.4 is 23 degrees not 0.45 degrees as I thought (the radians on top). So sorry for the inconvenience if anyone is answering this! (But if you are and you notice this, please answer anyways as any knowledge on the subject is needed for me!) I still don't understand the plus minus thing.
• Mar 31st 2013, 04:52 PM
Soroban
Re: Am I or the book wrong?
Hello, Paze!

Quote:

Solve in radians:. $\sin x\,=\,0.4$

The book claims: . $\begin{Bmatrix}0.41+2\pi n \\ 2.73+2\pi n \end{Bmatrix}$

I don't understand why the book does only plus, and not plus/minus.

The $n$ they use is traditionally defined to be an integer,
. . a positive or negative whole number.

• Mar 31st 2013, 04:55 PM
Paze
Re: Am I or the book wrong?
Yea I came to think of that later on. I just seem to remember it being +/- for some reason...