# I get the error "Undefined function 'symsum' for input arguments of type 'double'. while solving the equation given below.Please help me.

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clc
clear all
syms m x k
m=5;
k=2;
alpha=2;
beta=(1.65)*(10^(-5));
sai=10;
rho=15;
pt=2;
pn=16.56*10^(-14);
g = @(x)symsum((((1/factorial(k))*(m*sai*pn/2*beta)^k)),k,0,m-1).*exp(-(rho.*x)+((m*sai*pn*x.^alpha)/(beta*pt)))*x.^(alpha*1);
format long
f= rho*integral(g,0,inf)
plot(alpha,f,'*')

Star Strider on 23 Feb 2020
This runs without error and then yields an infinite result:
syms m x k
m=sym(5);
% k=sym(2);
alpha=sym(2);
beta=sym(1.65E-5);
sai=sym(10);
rho=sym(15);
pt=sym(2);
pn=sym(16.56E-14);
g = symsum((((1/factorial(k))*(m*sai*pn/2*beta)^k)),k,0,m-1).*exp(-(rho.*x)+((m*sai*pn*x.^alpha)/(beta*pt)))*x.^(alpha*1);
f= rho*int(g,x,0,inf)
plot(alpha,f,'*')
I leave the rest to you.
Walter Roberson on 23 Feb 2020
syms k
k=2
But the second line removes the identity of k as a symbolic variable
PARVEEN KUMAR SINGHAL on 25 Feb 2020
Thankyou Very Much Sir. Really it solved my problem.

Cameron B on 23 Feb 2020
Edited: Cameron B on 23 Feb 2020
I ran the script below and got a very large answer. You should check my code/output as there may be a mistake (using matlab mobile and don’t have time to check it), but at least there’s no error.
clc
clear all
syms k x
m=5;
alpha=2;
beta=(1.65)*(10^(-5));
sai=10;
rho=15;
pt=2;
pn=16.56*10^(-14);
c=(m*sai*pn)/(beta*pt);
fun=exp(-1.*(rho.*x + c.*x.^alpha)).*x.^(alpha*k);
g = symsum(1/factorial(k).*c.^k.*rho.*int(fun,0,inf),k,0,m-1);
g=double(g);

R2019a

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