how to do matrix symbolic differentiation

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Aamna Alshehhi 2019-11-3

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https://ww2.mathworks.cn/matlabcentral/answers/488950-how-to-do-matrix-symbolic-differentiation

评论： Harsha Priya Daggubati 2019-11-6

在 MATLAB Online 中打开

so I wrote this to calucalte Om2 and OmA, using symbolic differentiation but I get an error saying

"Warning: Unable to find explicit solution.

> In solve (line 317)

In Gr_51_Aamna (line 72)

Error using solve>getEqns (line 404)

Input argument contains an empty equation or variable."

note that i already got Th2_2 and ThA_2 in separate matrices

Thanx in advance for any help..

% Parameters:
L1=1.8;
L3=2.4;
L2=2.2;
L4=2.7;
L1_2=1.18;
L2_2=0.467;
Th1= 134;
Th1_2=142.5;
v=0.0362;
for t=0:10
LA(:,t+1) = 1.15-(v*t);
end 
%Parameters 
syms L1 L2 L3 L4 L1_2 L2_2 Th1 Th1_2 integer
% variables and their derivatives
syms LA Th2_2 Om2 Al2 Th3_1 Om3 Al3 Th4_1 Om4 Al4 ThA_2 OmA AlA integer
%loop eqn. 
L_eqn1 = L2_2*exp(1i*Th2_2)+LA*exp(1i*ThA_2) -L1_2*exp(1i*Th1_2)==0;
L_eqn2 = L2*exp(1i*Th2_2)-L3*exp(1i*Th3_1)+L4*exp(1i*Th4_1) -L1*exp(1i*Th1)==0;
%velocity eqn for Om2 and OmA.
dL_eqn1 = diff(L_eqn1,Th2_2)*Om2 +diff(L_eqn1,ThA_2)*OmA+ v*t;
real_vel_eqn1 = real(dL_eqn1);
imag_vel_eqn1 = imag(dL_eqn1);
[Om2, OmA]=solve (real_vel_eqn1, imag_vel_eqn1);

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Harsha Priya Daggubati 2019-11-6

Hi,

I doubt you are giving wrong syntax to 'solve'. solve expects it's first argument to be an equation, which in your case is real part of the equation. I guess it is causing the error to popup. Refer to the following link for help:

https://www.mathworks.com/help/symbolic/solve.html

Hope this helps!

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