1. Oct 24, 2009

I'm not sure where to post this, so please excuse me if this is misplaced. I need help understanding how the terms are grouped in this formula for A = pressure normal to the roof. If any of you are familiar with this formula or can link me to a source containing better expressed formulas like this one I'd appreciate your help. I'm posting a screen shot of the formula from a textbook I'm looking at. It looks something like:
A = Fsinx^1.84cos-1

Apparently it's a formula belonging to someone called Charles Hutton and it looks something more like Pn= P(sinx)^(1.842cosx-1) I just want to double check whether the exponent is really (1.842cosx-1) and not something like 1.842cos(x-1).

http://i33.tinypic.com/13z6fqt.jpg

Last edited: Oct 24, 2009
2. Oct 24, 2009

### FredGarvin

I have never heard of it, but there is another source I found that references it as well (it even talks about the experimental basis for the equation):

http://www.archive.org/stream/sixmonographsonw00flemrich/sixmonographsonw00flemrich_djvu.txt

3. Oct 24, 2009

### nvn

cuad: First, from other sources, we know your attached image in post 1 is missing parentheses around sin theta. Secondly, because addition and subtraction have a low precedence of arithmetic operations, unlike multiplication, we know addition and subtraction expressions can be passed to a function only if the addition or subtraction expression argument is enclosed in parentheses, such as cos(x - 1). Therefore, we know the formula is Pn = P*(sin theta)^[(1.842*cos theta) - 1].

4. Oct 24, 2009