May 11th, 2018, 08:23 PM  #1 
Newbie Joined: Aug 2017 From: India Posts: 15 Thanks: 0  Negative Theta Angle
If you take a circle, the angle theta varies from 0 to 360 Degrees. What exactly is negative angle like 30 etc? I mean to say 330 is also 30 degrees? I am confused?
Last edited by skipjack; May 12th, 2018 at 05:34 AM. 
May 11th, 2018, 08:57 PM  #2 
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,807 Thanks: 1045 Math Focus: Elementary mathematics and beyond 
The sign of an angle is generally taken to be the direction from 0$^\circ$ with a negative value indicating clockwise motion.

May 11th, 2018, 09:16 PM  #3 
Newbie Joined: Aug 2017 From: India Posts: 15 Thanks: 0 
So if I correctly understand, 0 to 360 degrees is counter clockwise direction and 0 to 360 (20 etc.) is clockwise direction. Am I correct?
Last edited by skipjack; May 12th, 2018 at 05:19 AM. 
May 11th, 2018, 09:24 PM  #4 
Senior Member Joined: Nov 2010 From: Indonesia Posts: 1,952 Thanks: 132 Math Focus: Trigonometry  Yes.
Last edited by skipjack; May 12th, 2018 at 05:19 AM. 
May 11th, 2018, 09:29 PM  #5 
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,807 Thanks: 1045 Math Focus: Elementary mathematics and beyond  Yes. So $\cos270^\circ=\cos90^\circ$ or, more generally, $\cos\alpha=\cos(\alpha+360k),k\in\mathbb{Z}$.
Last edited by skipjack; May 12th, 2018 at 05:19 AM. 
May 12th, 2018, 05:34 AM  #6 
Global Moderator Joined: Dec 2006 Posts: 18,962 Thanks: 1606  
May 12th, 2018, 07:02 PM  #7 
Newbie Joined: Aug 2017 From: India Posts: 15 Thanks: 0  Is it possible for you to give examples or links corresponding to them? Thank you.
Last edited by greg1313; May 12th, 2018 at 07:20 PM. 
May 14th, 2018, 02:24 AM  #9 
Newbie Joined: Aug 2017 From: India Posts: 15 Thanks: 0 
My requirement is a kind of creation of sine wave using a look up table. So the 360 degrees is represented as 65536 an int value. The sampling frequency is the frequency of the pwm signal which 20KHz. I need to write a program for the same. I do not know what is the use of this sampling frequency. Why is it required? Please advise.


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