Equation help with trig functions

1. Oct 23, 2012

vysero

I am currently working a physics problem and I have run into some math that I don't understand.

y = 4.0m + 4.0m(sin theta) = 4.0m(1+sin(theta))

In the problem I am trying to find a specific height at a certain angle (pendulum problem). I have found some help online that walks me through each step of the problem. I am just trying to understand how the above equation works, specifically the last part how 4 + 4(sin (theta)) is somehow equivalent to 4(1+sin(theta)). Is this some application of a formula or simple algebra that I am not understanding?

Maybe if you need more info you could check out the problem if you want too. The problem is located here: http://iweb.tntech.edu/murdock/books/v1chap6.pdf (Scroll down to page 143, worked examples # 6.2)

2. Oct 23, 2012

Staff: Mentor

This is nothing more than the distributive property.

a*b + a*c = a * (b + c)

3. Oct 23, 2012

vysero

Okay so that's good to know. I am still a little confused. Why does the 4.0m turn into 1? For instance if I have (4+4)(x) I get 4x + 4x which equals 8x right? So maybe this is not the distributive property but if I have (4 +4)(sin(theta)) would that not be 4sin(theta) + 4sin(theta) which = 8sin(theta).. guess I still don't understand.

4. Oct 23, 2012

Staff: Mentor

Here's a cleaned up version of what you write in post #1.
When you're doing algebra, you should get rid of the units. They don't add anything useful, and can cause confusion.

4 + 4sin(theta) = 4*1 + 4* sin(theta) = 4 * (1 + sin(theta))

Let's make it real simple, and get rid of the trig stuff.

4 + 4x = 4*1 + 4*x = 4(1 + x)
Get it?

5. Oct 23, 2012

vysero

Awesome, thank you that's exactly what I needed to see.