April 9th, 2018, 06:10 AM  #1 
Member Joined: Jan 2016 From: Uk Posts: 80 Thanks: 2  ARCTAN Equation distilled
Hi, I've been given an equation for use in a project. The system has limitations, e,g, it doesn't support '^' Here is the equation: arctn= x/y/( 1+0.28125*( x/y )^2)*180/pi Firstly does it look ok as an approximation of ARCTAN? Second, is it possible to remove all brackets to show me the sequence of events, please? Camerart Last edited by skipjack; April 9th, 2018 at 07:38 AM. 
April 9th, 2018, 07:39 AM  #2 
Global Moderator Joined: Dec 2006 Posts: 19,865 Thanks: 1833 
What is the argument of arctan?

April 9th, 2018, 09:40 AM  #3 
Member Joined: Jan 2016 From: Uk Posts: 80 Thanks: 2  
April 9th, 2018, 05:54 PM  #4 
Global Moderator Joined: Dec 2006 Posts: 19,865 Thanks: 1833 
If x/y = 1, what value should the arctan have and what does the formula give? Now try another value for x/y, such as 0.5.

April 10th, 2018, 01:37 AM  #5  
Member Joined: Jan 2016 From: Uk Posts: 80 Thanks: 2  Quote:
Someone on a programming forum, has done this for me as I'm a bit of a dunce when it comes to maths and trigonometry, but to add to my confusion, I think he reversed X and Y. I actually only want to see the equation distilled to without brackets, if possible, so I can work out how it works. C.  
April 10th, 2018, 07:56 AM  #6 
Global Moderator Joined: Dec 2006 Posts: 19,865 Thanks: 1833 
arctan(u) = u/(1 + 0.28125u²) is a reasonable approximation for u < 1. So is arctan(u) = u/(1 + 0.282u²). The above both give a result in radians, so multiplying by 180$^\circ$/pi gives the value in degrees. 
April 10th, 2018, 10:13 AM  #7  
Member Joined: Jan 2016 From: Uk Posts: 80 Thanks: 2  Quote:
The original equation is working, but I'll try your neater version tomorrow, thanks. C.  

Tags 
arctan, distilled, equation 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
arctan(tan(5pi/8))  JPow  Trigonometry  3  November 1st, 2017 12:50 PM 
arctan(x)= infinity?  fromage  Calculus  4  May 16th, 2015 04:11 AM 
arctan...  ungeheuer  Calculus  3  January 16th, 2013 05:17 AM 
arctan  danneman91  Algebra  2  October 3rd, 2011 01:11 PM 
Solving arctan( k * x ) + x = c  HenrikAndresen  Complex Analysis  2  October 26th, 2009 01:22 AM 