MATLAB: I was wondering if anyone could help me solve these three simultaneous equations

equationfsolvesimultaneoussolvesyms

The constants are listed and I'm trying to use the 'syms' and 'solve' commands. I want to try and solve them for a, b and c. The three equations are inside the 'solve'. When I run it it just seems to give errors on lines that don't even exist. My code so far is as follows:

H=14;
K=24.66;
L=80;
D=60;
syms a b c ;
S=solve([H == a+(exp(b*c) + exp(-b*c))/(2*b),  K== a  +(exp(b(D-c)) + exp(-b(D-c)))/(2*b),L == (exp(b(D-c)) - exp(-b(D-c)) + exp(b*c) - exp(-b*c))/(2*b)], [a, b, c])

Best Answer

You missed some multiplication symbols. In MATLAB, b(D-c) means b indexed at D-c or b called with parameter D-c . You want b*(D-c)

Related Solutions

MATLAB: Linsolve doesn’t find solution to overdetermined system

Linsolve will try to solve only for those variables that you specify as unknowns. The rest are treated as constants. So, the things you call "constraints" like D = 2 A + 3 B + 10 C are not valid when the only specified unknowns are x,y,z because constraints cannot be imposed on constants.

Your first failed case happens because a solution to all 4 equations cannot be found when x,y,z are the only free variables. In the second case, the solution is indeed not unique, because you have 4 equations and 7 unknowns.

However, you can get the effect you want by using a different solver,

s=solve([eqn1,eqn2,eqn3,eqn4])

MATLAB: Need solution with symbolic

Here:

Z2(z2)=piecewise(0<=z2, z2, 0>z2, 0.2*(exp(z2)-1));
  %^

z2 is not an independent symbolic variable. It is a symbolic expression. You should use the base variables to make symbolic functions. For example

syms  w12 a1 b12 z2 
z2 = w12*a1 + b12;
Z2(w12,a1,b12)=piecewise(0<=z2, z2, 0>z2, 0.2*(exp(z2)-1));
Z2(10, 1, 2)

Best Answer

Related Solutions

MATLAB: Linsolve doesn’t find solution to overdetermined system

MATLAB: Need solution with symbolic

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