How can I simplify the symbolic expressions?

Question

Ali Almakhmari 2023-9-11

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2019426-how-can-i-simplify-the-symbolic-expressions

编辑： Ali Almakhmari 2023-9-11

I hate the fact that solve keeps outputting symbolic expressions with extremely large numbers, when clearly it can simplify further and get rid of those numbers. How can I force it to do that? Its okay with me if I can get an approximation up 6 decimal places.

clear

clc

syms q_bar delta_o theta1 theta2 q S CL_alpha CL_delta b e KT

eqn1 = (2*theta1 - theta2 - q_bar.*theta1 + q_bar.*theta2) == (-0.4805020381.*q_bar.*delta_o);

eqn2 = (-theta1 + theta2 - 2.*q_bar.*theta2) == (-0.0051005137.*q_bar.*delta_o);

sol = solve(eqn1,eqn2,theta1,theta2);

L1 = q.*S.*CL_alpha.*sol.theta1;

L2 = q.*S.*CL_alpha.*sol.theta2 + q.*S.*CL_delta.*delta_o;

eqn1 = (0.25.*L1.*b + 0.75.*L2.*b) == 0;

a=solve(eqn1,q_bar)

a =

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Torsten 2023-9-11

在 MATLAB Online 中打开

If you need 6 decimal places, why do you supply model parameters with 10 decimal places ?

-0.4805020381*q_bar
-0.0051005137*q_bar

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

John D'Errico 2023-9-11

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2019426-how-can-i-simplify-the-symbolic-expressions#answer_1307161

编辑：John D'Errico 2023-9-11

在 MATLAB Online 中打开

clear

clc

syms q_bar delta_o theta1 theta2 q S CL_alpha CL_delta b e KT

eqn1 = (2*theta1 - theta2 - q_bar.*theta1 + q_bar.*theta2) == (-0.4805020381.*q_bar.*delta_o);

eqn2 = (-theta1 + theta2 - 2.*q_bar.*theta2) == (-0.0051005137.*q_bar.*delta_o);

sol = solve(eqn1,eqn2,theta1,theta2);

L1 = q.*S.*CL_alpha.*sol.theta1;

L2 = q.*S.*CL_alpha.*sol.theta2 + q.*S.*CL_delta.*delta_o;

eqn1 = (0.25.*L1.*b + 0.75.*L2.*b) == 0;

a=solve(eqn1,q_bar)

a =

They are simple already. At least, as simple as they can be. You have unknowns in there, inside and outside of the square roots. I suppose you could play around, and make it different, but simpify will not find anything glaring to reduce there.

Can you make the numbers smaller? Well, yes, you can force VPA to round them.

vpa(a,10)

ans =

Is that simpler? I guess.

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Ali Almakhmari 2023-9-11

编辑：Ali Almakhmari 2023-9-11

Not really. I mean, you can take 5.642719936e17 in common from numerator and denominator and have everything simplify to have all numbers between 0.1 to 10 instead of so complicated like that with high numbers.

请先登录，再进行评论。