# Trig question

1. Oct 17, 2016

### quicksilver123

1. The problem statement, all variables and given/known data

my book shows:

(-1/(1-((b+acosx)/(a+bcosx))^2)^1/2) * ((a+bcosx)(-asinx)-(b+acosx)(-bsinx))/(a+bcosx)^2

=
(a^2+b^2cos^2(x)-b^2-a^2cos^2(x))^(-1/2)
*
((a^2-b^2)sinx/(| a+bcosx |))

I'm having a hard time understanding how they did this.

Last edited: Oct 17, 2016
2. Oct 17, 2016

### FactChecker

Please proof read your equation. I see a variable c on the left side and a variable A on the right that is not matched on the other side. What are they?

3. Oct 17, 2016

### quicksilver123

Edited. Thanks for the heads up, "c" was a typo

4. Oct 18, 2016

### Kara386

It's really hard to read your equation. Do you know how to use LaTeX? There's a tutorial here: https://www.physicsforums.com/help/latexhelp/
But in the meantime, is this what you meant?

$\frac{-1}{\sqrt{1-(\frac{b+a\cos(x)}{a+b\cos(x)})^2}} \frac{(a+b\cos(x))(-a\sin(x))-(b+a\cos(x))(-b\sin(x))}{(a+b\cos(x))^2} = \frac{1}{\sqrt{a^2+b^2\cos^2(x)-b^2-a^2\cos^2(x)}} \frac{(a^2-b^2)\sin(x)}{|a+b\cos(x)|}$

Admittedly that's quite tricky to format, brackets don't enclose the fraction and that type of thing, someone might have suggestions on how to improve on it.

5. Oct 18, 2016

### quicksilver123

Thanks!

Actually this is what I meant. I copy and pasted and edited your latex script.