Sym equation to double

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Dallin Porter
Dallin Porter 2021-2-15
评论： Star Strider 2021-2-15
I have an equation, y == 319.242, saved as a symbolic variable, and want to use this vlaue as a variable, y. How do I convert the symbolic equation to a variable?
Here's what I have so far. I'm probably doing this the worst way possible, so any help is appreciated.
syms y
theta=60;
r=y/sind(theta);
x=r*cosd(theta);
eqn=y==600-x^2/121;
eqn=isolate(eqn,y);
y=vpa(eqn); %This is where I'm stuck. I don't know how to convert the equation to a double to use in the next equation.
x=y*cotd(theta);
x=vpa(x);
scatter(x,y)

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采纳的回答

Star Strider
Star Strider 2021-2-15
There are 2 values for ‘y’, so use solve rather than isolate to calculate them:
syms y
theta=60;
r=y/sind(theta);
x=r*cosd(theta);
eqn=y==600-x^2/121;
% eqn=isolate(eqn,y)
eqn = solve(eqn,y)
y=vpa(eqn);
x=y*cotd(theta);
x=vpa(x);
scatter(x,y)
.
  2 个评论
Dallin Porter
Dallin Porter 2021-2-15
Thank you. That's exactly what I needed.
Star Strider
Star Strider 2021-2-15
As always, my pleasure!

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更多回答（1 个）

David Hill
David Hill 2021-2-15
theta=60;
fun=@(x)600-(x*cotd(theta))^2/121-x;
y=fsolve(fun,300);
x=y*cotd(theta);
scatter(x,y);

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