# What does a comma mean in a trig formula?

• Feb 22nd 2009, 02:16 AM
haydnw
What does a comma mean in a trig formula?
Hi,

I'm trying to use an equation an astronomy website (eq. 23), but it contains a comma and I'm not sure why / what it means! The equation is:

Code:

`A = arctan(sin H, cos H sin φ − tan δ cos φ)`
I know the values of H, φ and δ, but I don't know what to do about the comma. Their working, given using the values previously worked out, is:

Code:

```A = arctan(sin(3.7838°), cos(3.7838°) * sin(52°) − tan(4.7585°) * cos(52°)) = 5.1302°```
Obviously that still includes the comma, with no clue to it's meaning! Any suggestions whatsoever would be very much appreciated! (Happy)

EDIT: I've put this in the High School forum as the actual trig isn't that difficult - I have no idea how difficult the comma is, so didn't really know where else to post it anyway! Hope that's OK.
• Feb 22nd 2009, 02:20 AM
Moo
Hello,
Quote:

Originally Posted by haydnw
Hi,

I'm trying to use an equation an astronomy website (eq. 23), but it contains a comma and I'm not sure why / what it means! The equation is:

Code:

`A = arctan(sin H, cos H sin φ − tan δ cos φ)`
I know the values of H, φ and δ, but I don't know what to do about the comma. Their working, given using the values previously worked out, is:

Code:

```A = arctan(sin(3.7838°), cos(3.7838°) * sin(52°) − tan(4.7585°) * cos(52°)) = 5.1302°```
Obviously that still includes the comma, with no clue to it's meaning! Any suggestions whatsoever would be very much appreciated! (Happy)

EDIT: I've put this in the High School forum as the actual trig isn't that difficult - I have no idea how difficult the comma is, so didn't really know where else to post it anyway! Hope that's OK.

Well, they defined it (Surprised)

Click on the arctan (which is highlighted in blue) and you will be referred to a list of notations among which :
Quote:

arctan(y,x) the angle between the [x]-axis and the line from [(0,0)] to [(x,y)]
• Feb 22nd 2009, 02:57 AM
haydnw
Quote:

Originally Posted by Moo
Well, they defined it

(Headbang) I can't believe I missed that! Thank you very much - it all makes sense now. As a tangent - pun not intended - this translates to the atan2() function in several different computer programming languages.