March 1st, 2017, 08:21 PM  #1 
Newbie Joined: Mar 2017 From: United States Posts: 8 Thanks: 0  How to calculate the 'VALUE' of a point on a circle?
The value of point A = 2 @ 0 degrees The value of point B = 6 @ 180 degrees How to calculate the value of point C = ? @ 120 degrees I have a computer program that returns point C = 4.57735 Can anyone PLEASE show me this math using calculator functions? Thank you so much for any help! 
March 2nd, 2017, 06:07 AM  #2 
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,434 Thanks: 870 Math Focus: Elementary mathematics and beyond 
You're going to have to offer a better explanation of what it is that you are trying to do, at least as far as I am concerned.

March 2nd, 2017, 06:56 AM  #3 
Senior Member Joined: Apr 2014 From: Glasgow Posts: 1,926 Thanks: 628 Math Focus: Physics, mathematical modelling, numerical and computational solutions 
Yep... we need more information to give you anything meaningful.

March 2nd, 2017, 07:40 AM  #4 
Newbie Joined: Feb 2017 From: Netherlands Posts: 8 Thanks: 2 Math Focus: Trigonometry and complex numbers 
Shouldn't it be $\displaystyle 4\frac{2}3$?
Last edited by Xxmarijnw; March 2nd, 2017 at 07:42 AM. 
March 2nd, 2017, 09:00 AM  #5 
Newbie Joined: Mar 2017 From: United States Posts: 8 Thanks: 0 
Thank you greg1313 and Benit13 for responding, CIRCLE values are: 0 degrees = 0 45 degrees = 1 90 degrees = 2 180 degrees = 4 360 degrees = 8 Sorry if I misrepresented the starting point value of 2 being at 0 degrees on the circle. What I meant was 0 degrees as my starting point which is @ 90 degrees on the circle TO 120 degrees as my ending point which is @ 210 degrees on the circle. Trying to understand why 120 degrees doesn't equal 8 / 3 + 2. Can anyone think of a formula as to how my computer program is calculating 4.57735 ? I can confirm that the generated value of 4.57735 is correct in my application. 
March 2nd, 2017, 09:30 AM  #6 
Senior Member Joined: Apr 2014 From: Glasgow Posts: 1,926 Thanks: 628 Math Focus: Physics, mathematical modelling, numerical and computational solutions 
What is your program for? What is it trying to work out? Is CIRCLE a subroutine? If so, can you post the source code for that specific routine here?

March 2nd, 2017, 10:18 AM  #7  
Math Team Joined: Jul 2011 From: Texas Posts: 2,422 Thanks: 1189  Quote:
$v = \dfrac{\theta}{45}$ where $v$ is the "value" (whatever that means) and $\theta$ is the angle in degrees so, $\dfrac{120}{45} = \dfrac{8}{3}$  
March 2nd, 2017, 10:26 AM  #8 
Senior Member Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,155 Thanks: 461 Math Focus: Calculus/ODEs 
It seems to me, from the data provided, that the "circle value" $\displaystyle C$ can be expressed as a function of the angle $\displaystyle \theta$ as follows: $\displaystyle C(\theta)=\frac{\theta}{45^{\circ}}$ And so, as you found: $\displaystyle C(210^{\circ})=\frac{210^{\circ}}{45^{\circ}}= \frac{14}{3}$ 
March 2nd, 2017, 11:04 AM  #9 
Newbie Joined: Mar 2017 From: United States Posts: 8 Thanks: 0 
Sorry Benit13, I don't have the source code, but here are some other values generated from the software: 45 degrees from value 2 = 3.0 90 degrees from value 2 = 4.0 120 degrees from value 2 = 4.57735 180 degrees from value 2 = 6.0 240 degrees from value 2 = 7.42265 The 45, 90 and 180 degrees makes logical sense, but not the 120 and 240. 45 = 1 + 2 90 = 2 + 2 180 = 4 + 2 There has to be a formula for the 120 and 240 calculations that I'll probably never work out. Thank you everyone for your time and effort! 
March 2nd, 2017, 05:50 PM  #10 
Global Moderator Joined: Dec 2006 Posts: 16,775 Thanks: 1234 
Note that 4.57735... = 4 + 1/√3 and 7.42265... = 8  1/√3, and that tan(30°) = 1/√3.


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