Directed Angle

For students of class 9-10 (age 14-16)
tanmoy
Posts:312
Joined:Fri Oct 18, 2013 11:56 pm
Location:Rangpur,Bangladesh
Directed Angle

Unread post by tanmoy » Tue Sep 30, 2014 11:17 pm

What is directed angle :?:
"Questions we can't answer are far better than answers we can't question"

User avatar
Phlembac Adib Hasan
Posts:1016
Joined:Tue Nov 22, 2011 7:49 pm
Location:127.0.0.1
Contact:

Re: Directed Angle

Unread post by Phlembac Adib Hasan » Wed Oct 01, 2014 8:52 am

It means the angle has an orientation based value, i.e. $\angle ABC=-\angle CBA$ Also see former $9-10$ Higher Math Geo book. In the beginning of trigonometry, there is a section about signed angles.

Also for simplicity, sometimes mod $\pi$ redian is also used. In that case $\pi - \angle ABC\equiv -\angle ABC\equiv \angle CBA\pmod \pi$

This is not a olympiad level question. So moving it to secondary.
Welcome to BdMO Online Forum. Check out Forum Guides & Rules

User avatar
*Mahi*
Posts:1175
Joined:Wed Dec 29, 2010 12:46 pm
Location:23.786228,90.354974
Contact:

Re: Directed Angle

Unread post by *Mahi* » Wed Oct 01, 2014 7:21 pm

To add just a little to what Adib said-
Anti-clockwise = positive, Clockwise = negative is the general convention while using the +/- sign.
I was going to post a link here but didn't find anything well-explained enough in google (at least in the first few links).
Please read Forum Guide and Rules before you post.

Use $L^AT_EX$, It makes our work a lot easier!

Nur Muhammad Shafiullah | Mahi

User avatar
sowmitra
Posts:155
Joined:Tue Mar 20, 2012 12:55 am
Location:Mirpur, Dhaka, Bangladesh

Re: Directed Angle

Unread post by sowmitra » Fri Oct 03, 2014 11:04 pm

I think this might help...
Courtesy of R. A. Johnson, MAA, and, JSTOR :
http://www.jstor.org/stable/2973001

Post Reply