MATLAB unable to solve 6 equations :S

[sgvaibhav]

Hi,
I was solving questions on engineering mechanics
I came up with 6 equations and 6 unkowns

I used the solve function, but its not giving me the proper answer (it works very will with 3 unknowns and 3 equations)

This is my input

syms AX AY BX BZ CY CZ
Fx = sym('AX + BY = -125');
Fy = sym('AY + CY = 59');
Fz = sym('BZ + CZ = 388.87');

Mx = sym('-0.3*BZ - 0.4*AY = -212.2');
My = sym('0.5*CZ + 0.4*AX = 0');
Mz = sym('-0.5*CY + 0.3*BX + 0.5*AX = 0');

[AX,AY,BX,BZ,CY,CZ] = solve(Fx,Fy,Fz,Mx,My,Mz)
_____________________________________________________________
This is my output

AX =

398.07916666666666666666666666667-1.6666666666666666666666666666667*AY



AY =

1.1111111111111111111111111111111*AY-565.13194444444444444444444444444



BX =

-523.07916666666666666666666666667+1.6666666666666666666666666666667*AY



BZ =

-1.3333333333333333333333333333333*AY+707.33333333333333333333333333333



CY =

-1.*AY+59.



CZ =

-318.46333333333333333333333333333+1.3333333333333333333333333333333*AY

___________________________________
How is that happening?

 

[sgvaibhav]

or is it that some other function has to be used other than solve?

 

[Cvan]

6 equations and 7 unknowns? You don't declare B_y in your initial syms statement, but it probably gets declared when it's used below. Maybe the coffee hasn't kicked in for me yet so feel free to tell me I'm an idiot :D, but that's what pops out to me right now.

 

[sgvaibhav]

6 equations and 7 unknowns? You don't declare B_y in your initial syms statement, but it probably gets declared when it's used below. Maybe the coffee hasn't kicked in for me yet so feel free to tell me I'm an idiot :D, but that's what pops out to me right now.

oops i just realized i have 7 unknowns :S :S :S
and also that i forgot to declare BY.
something wrong with the equations...

lol, my exam is over for engineering mechanics :P, I am not going back to check for the correct stuff now.

 

[blue_raver22]

I would first suggest checking your input and equations to make sure they are correct. It is possible that there may be an error in the equations or a typo in the input that is causing the unexpected output.

If the equations and input are correct, then it is possible that there may not be a unique solution to the system of equations. In this case, MATLAB may be giving you a general solution with some unknown variables. You can try using the "assume" function to specify any assumptions about the variables, which may help narrow down the solution.

It is also possible that the equations are not linearly independent, meaning that some of the equations can be derived from the others. In this case, the system may have infinite solutions or no solutions at all.

If none of these explanations seem to apply, it may be helpful to consult with a colleague or seek assistance from MATLAB support to further troubleshoot the issue.