why do I get the wrong angle

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Sarah Alhabbas
Sarah Alhabbas on 14 Jun 2022
Commented: Torsten on 14 Jun 2022
why do i keep getting a negatie value for angle

Answers (1)

David Hill
David Hill on 14 Jun 2022
Edited: David Hill on 14 Jun 2022
Recommend avoiding using symbolics. Seeking numerical solution, use fzero.
mo=2.5;
y=1.4;
angle=10;
fun=@(a)((2*(1+((y-1)/2)*mo^2*(sind(a)).^2))./(((y+1)*mo^2*sind(a).*cosd(a))))-tand(a-angle);
A=fzero(fun,32);
  3 Comments
David Hill
David Hill on 14 Jun 2022
You could also plot and see that there are two solutions between (0 - 90).
mo=2.5;
y=1.4;
angle=10;
fun=@(a)((2*(1+((y-1)/2)*mo^2*(sind(a)).^2))./(((y+1)*mo^2*sind(a).*cosd(a))))-tand(a-angle);
x=3:.1:87;
plot(x,fun(x));
David Hill
David Hill on 14 Jun 2022
Edited: David Hill on 14 Jun 2022
When you graph the function you see solutions should be around 30 and 80. fzero requires an initial guess. 32 is not an exact solution.
mo=2.5;
y=1.4;
angle=10;
fun=@(a)((2*(1+((y-1)/2)*mo^2*(sind(a)).^2))./(((y+1)*mo^2*sind(a).*cosd(a))))-tand(a-angle);
A=fzero(fun,30)
A = 31.8506
mo=2.5;
y=1.4;
angle=10;
fun=@(a)((2*(1+((y-1)/2)*mo^2*(sind(a)).^2))./(((y+1)*mo^2*sind(a).*cosd(a))))-tand(a-angle);
A=fzero(fun,80)
A = 85.5761

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