converting sym to double

[ekrem]

Hello everyone,

I am trying to evaluate the numerical value of r. It gives the following error.How can I convert r to a double variable?

r = int('a*sin(b*x)')
r =

-(a*cos(b*x))/b

a=3

a =

3

b=4

b =

4

x=7

x =

7

double(r)

??? Error using ==> mupadmex
Error in MuPAD command: DOUBLE cannot convert the input expression into a double array.

If the input expression contains a symbolic variable, use the VPA function instead.

Error in ==> sym.sym>sym.double at 927
Xstr = mupadmex('mllib::double', S.s, 0);

[Wayne King]

Post by ekrem
Hello everyone,
I am trying to evaluate the numerical value of r. It gives the following error.How can I convert r to a double variable?
r = int('a*sin(b*x)')
r =
-(a*cos(b*x))/b

a=3

a =
3

b=4

b =
4

x=7

x =
7

double(r)

??? Error using ==> mupadmex
Error in MuPAD command: DOUBLE cannot convert the input expression into a double array.
If the input expression contains a symbolic variable, use the VPA function instead.
Error in ==> sym.sym>sym.double at 927
Xstr = mupadmex('mllib::double', S.s, 0);

Hi, Are you trying to evaluate your antiderivative at a point? Use subs()

syms x
r = int(3*sin(4*x));
subs(r,7)


Wayne

[ekrem]

Post by Wayne King

Post by ekrem
Hello everyone,
I am trying to evaluate the numerical value of r. It gives the following error.How can I convert r to a double variable?
r = int('a*sin(b*x)')
r =
-(a*cos(b*x))/b

a=3

a =
3

b=4

b =
4

x=7

x =
7

double(r)

??? Error using ==> mupadmex
Error in MuPAD command: DOUBLE cannot convert the input expression into a double array.
If the input expression contains a symbolic variable, use the VPA function instead.
Error in ==> sym.sym>sym.double at 927
Xstr = mupadmex('mllib::double', S.s, 0);

Hi, Are you trying to evaluate your antiderivative at a point? Use subs()

syms x

Post by Wayne King
r = int(3*sin(4*x));
subs(r,7)
Wayne

Hey, Thanks a lot. It's helping and I am trying.

But I have a new problem.

what if,

I want to find r when,
r = int(y*sin(4*x)); ??

Should I do this;
syms x
syms y

Post by Wayne King
r = int(y*sin(4*x));
subs(r,7,5) ??

Thanks!!

[Wayne King]

Post by Wayne King

Post by Wayne King

Post by ekrem
Hello everyone,
I am trying to evaluate the numerical value of r. It gives the following error.How can I convert r to a double variable?
r = int('a*sin(b*x)')
r =
-(a*cos(b*x))/b

a=3

a =
3

b=4

b =
4

x=7

x =
7

double(r)

??? Error using ==> mupadmex
Error in MuPAD command: DOUBLE cannot convert the input expression into a double array.
If the input expression contains a symbolic variable, use the VPA function instead.
Error in ==> sym.sym>sym.double at 927
Xstr = mupadmex('mllib::double', S.s, 0);

Hi, Are you trying to evaluate your antiderivative at a point? Use subs()

syms x

Post by Wayne King
r = int(3*sin(4*x));
subs(r,7)
Wayne

Hey, Thanks a lot. It's helping and I am trying.
But I have a new problem.
what if,
I want to find r when,
r = int(y*sin(4*x)); ??
Should I do this;
syms x
syms y

Post by Wayne King
r = int(y*sin(4*x));
subs(r,7,5) ??

Thanks!!

Hi Ekrem, I'm assuming you want to integrate with respect to x in the above

syms x y;
r = int(y*sin(4*x),x);
x = 7;
y = 5;
subs(r)

Wayne

[ekrem]

Post by Wayne King

Post by ekrem
Hello everyone,
I am trying to evaluate the numerical value of r. It gives the following error.How can I convert r to a double variable?
r = int('a*sin(b*x)')
r =
-(a*cos(b*x))/b

a=3

a =
3

b=4

b =
4

x=7

x =
7

double(r)

??? Error using ==> mupadmex
Error in MuPAD command: DOUBLE cannot convert the input expression into a double array.
If the input expression contains a symbolic variable, use the VPA function instead.
Error in ==> sym.sym>sym.double at 927
Xstr = mupadmex('mllib::double', S.s, 0);

Hi, Are you trying to evaluate your antiderivative at a point? Use subs()
syms x
r = int(3*sin(4*x));
subs(r,7)
Wayne

Hey, thanks a lot!!
Now I got it.