I want to use atan2 in my equation. When I use atan2 , I get answer NaN. But when I use 'atan' , i didn't get NaN. Why?

7 views (last 30 days)
clear all
clc
syms alpha1 alpha1_d alpha1_dd
a=3;
b=2;
th1=atan2(a*sin(alpha1),(b*cos(alpha1)));
l1=a*cos(alpha1)*sin(th1)-b*sin(alpha1)*cos(th1);
l1_d=diff(l1,alpha1)*alpha1_d; % fisrt derivative of l1
l1_dd=jacobian(l1_d,[alpha1,alpha1_d])*[alpha1_d;alpha1_dd];% Sencond derivative of l1
% subs alpha1=0.5236, alpha1_d=0.2, alpha1_dd=0.01
L_dd=subs(l1_dd,[alpha1,alpha1_d,alpha1_dd],[0.5236,0.2,0.01]);
% Ans L_dd=NaN
%%%% when I replace atan2 by atan
clear all
clc
syms alpha1 alpha1_d alpha1_dd
a=3;
b=2;
th1=atan(a*sin(alpha1)/(b*cos(alpha1)));
l1=a*cos(alpha1)*sin(th1)-b*sin(alpha1)*cos(th1);
l1_d=diff(l1,alpha1)*alpha1_d;% fisrt derivative of l1
l1_dd=jacobian(l1_d,[alpha1,alpha1_d])*[alpha1_d;alpha1_dd];% Sencond derivative of l1
% subs alpha1=0.5236, alpha1_d=0.2, alpha1_dd=0.01
L_dd=double(subs(l1_dd,[alpha1,alpha1_d,alpha1_dd],[0.5236,0.2,0.01]));
% Ans L_dd=-0.1789

Accepted Answer

Swatantra Mahato
Swatantra Mahato on 19 Feb 2021
Edited: Swatantra Mahato on 19 Feb 2021
Hi Vishal,
You can try with "atan2" after making the following modifications
syms alpha1 alpha1_d alpha1_dd real
and add the line
l1=rewrite(l1,'sqrt');
before the line
l1_d=diff(l1,alpha1)*alpha1_d;
I have brought the issue to the notice of our developers. They will investigate the matter futher
Hope this helps
  3 Comments

Sign in to comment.

More Answers (0)

Categories

Products


Release

R2019b

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!