Incorrect Calculation when using symunit in Symbolic Math Toolbox
clc,clear
syms x a
u = symunit;
a = 1.01325*u.bar
b = -0.049576382*u.bar*u.m^3/u.mol
c = .000003657553277*u.bar*u.m^6/(u.mol)^2
d = -.00000000015676624*u.bar*u.m^9/u.mol^3
eqn = a*x^3+b*x^2+c*x+b == 0
solve(eqn,x,"MaxDegree",3)
vpa(solve(eqn,x,’MaxDegr
Output: 0.016
clc,clear
syms x
u = symunit;
a = 1.01325
b = -0.049576382
c = 3.657553277*10^-6
d = -1.5676624*10^-10
eqn = a*x^3+b*x^2+c*x+b == 0
solve(eqn,x,"MaxDegree",3)
vpa(solve(eqn,x,’MaxDegree’,3),10)
Output: 0.382
a = 1.01325
b = -0.049576382
c = 3.657553277*10^-6
d = -1.5676624*10^-10
x = [a b c d];
vpa(roots(x),10)
Output: 0.048
u = symunit;
a = 1.01325*u.bar
b = -0.049576382*u.bar*u.m^3/u.mol
c = .000003657553277*u.bar*u.m^6/(u.mol)^2
d = -.00000000015676624*u.bar*u.m^9/u.mol^3
x = [a b c d];
vpa(roots(x),10)
Output: root(z^3 – ((sym("223272175501577375")*z^2)/sym("4563272322433155072"))*(symunit("m")^3/symunit("mol")) + ((sym("539759593894213625")*z)/sym("149529307461489625399296"))*(symunit("m")^6/symunit("mol")^2) – sym("252691673573204875/1633258782299364015028043776")*(symunit("m")^9/symunit("mol")^3), z, 1)
Wolfram Alpha Answer: 0.048clc,clear
syms x a
u = symunit;
a = 1.01325*u.bar
b = -0.049576382*u.bar*u.m^3/u.mol
c = .000003657553277*u.bar*u.m^6/(u.mol)^2
d = -.00000000015676624*u.bar*u.m^9/u.mol^3
eqn = a*x^3+b*x^2+c*x+b == 0
solve(eqn,x,"MaxDegree",3)
vpa(solve(eqn,x,’MaxDegr
Output: 0.016
clc,clear
syms x
u = symunit;
a = 1.01325
b = -0.049576382
c = 3.657553277*10^-6
d = -1.5676624*10^-10
eqn = a*x^3+b*x^2+c*x+b == 0
solve(eqn,x,"MaxDegree",3)
vpa(solve(eqn,x,’MaxDegree’,3),10)
Output: 0.382
a = 1.01325
b = -0.049576382
c = 3.657553277*10^-6
d = -1.5676624*10^-10
x = [a b c d];
vpa(roots(x),10)
Output: 0.048
u = symunit;
a = 1.01325*u.bar
b = -0.049576382*u.bar*u.m^3/u.mol
c = .000003657553277*u.bar*u.m^6/(u.mol)^2
d = -.00000000015676624*u.bar*u.m^9/u.mol^3
x = [a b c d];
vpa(roots(x),10)
Output: root(z^3 – ((sym("223272175501577375")*z^2)/sym("4563272322433155072"))*(symunit("m")^3/symunit("mol")) + ((sym("539759593894213625")*z)/sym("149529307461489625399296"))*(symunit("m")^6/symunit("mol")^2) – sym("252691673573204875/1633258782299364015028043776")*(symunit("m")^9/symunit("mol")^3), z, 1)
Wolfram Alpha Answer: 0.048 clc,clear
syms x a
u = symunit;
a = 1.01325*u.bar
b = -0.049576382*u.bar*u.m^3/u.mol
c = .000003657553277*u.bar*u.m^6/(u.mol)^2
d = -.00000000015676624*u.bar*u.m^9/u.mol^3
eqn = a*x^3+b*x^2+c*x+b == 0
solve(eqn,x,"MaxDegree",3)
vpa(solve(eqn,x,’MaxDegr
Output: 0.016
clc,clear
syms x
u = symunit;
a = 1.01325
b = -0.049576382
c = 3.657553277*10^-6
d = -1.5676624*10^-10
eqn = a*x^3+b*x^2+c*x+b == 0
solve(eqn,x,"MaxDegree",3)
vpa(solve(eqn,x,’MaxDegree’,3),10)
Output: 0.382
a = 1.01325
b = -0.049576382
c = 3.657553277*10^-6
d = -1.5676624*10^-10
x = [a b c d];
vpa(roots(x),10)
Output: 0.048
u = symunit;
a = 1.01325*u.bar
b = -0.049576382*u.bar*u.m^3/u.mol
c = .000003657553277*u.bar*u.m^6/(u.mol)^2
d = -.00000000015676624*u.bar*u.m^9/u.mol^3
x = [a b c d];
vpa(roots(x),10)
Output: root(z^3 – ((sym("223272175501577375")*z^2)/sym("4563272322433155072"))*(symunit("m")^3/symunit("mol")) + ((sym("539759593894213625")*z)/sym("149529307461489625399296"))*(symunit("m")^6/symunit("mol")^2) – sym("252691673573204875/1633258782299364015028043776")*(symunit("m")^9/symunit("mol")^3), z, 1)
Wolfram Alpha Answer: 0.048 symunit, symbolic, cubic equation, units MATLAB Answers — New Questions