Conversion to logical from sym is not possible.

%% Solution using integration

% for this part you need to manually (by hand) integrate the moment equations twice and apply boundary conditions to arrive at the linear equations

syms c1 c2 c3 c4 c5 c6 c7 c8 %depend on number of equations which depends on number of segments of beam
eqn1= c5==0;
eqn2= (45/6)*5^3-(390/2)*5^2+c3*5+c7==0;
eqn3= (-7/3)*2^3-(5/12)*2^4+c1*2-c2==(-7/3)*2^3+15*2^2-(5/12)*2^4+c2*2+c6;
eqn4= (-7/3)*5^3+15*5^2-(5/12)*5^4+c2*5+c6==(45/6)*5^3-(390/2)*5^2+c3*5+c7;
eqn5= (45/6)*7^3-(390/2)*7^2+c3*7+c7==(25/6)*7^3-125*7^2+c4*7+c8;
eqn6= -7*2^2-(5/3)*2^3-c1==-7*2^2+30*2-(5/3)*2^3+c2;
eqn7= -7*5^2+30*5-(5/3)*5^3+c2==(45/2)*5^2-390*5+c3;
eqn8= (45/2)*7^2-390*7+c3==(25/2)*7^2-250*7+c4;

%ask matlab to prepare the matrices for you (linear equations Ax=b)
[A,B] = equationsToMatrix([eqn1, eqn2, eqn3, eqn4, eqn5, eqn6 , eqn7 , eqn8 ], [ c1 , c2 , c3 ,c4,c5,c6,c7,c8]);

C = double(linsolve(A,B));

syms x
first_segment_EIv= vpa((-5/9*x^4+-7/3*x^3+C(1)*x+C(5)),4);
second_segment_EIv= vpa((15*x^2-7/3*x^3-5/12*x^4+C(2)*x+C(6)),4); 
third_segment_EIv= vpa((-390/2*x^2+45/6*x^3+C(3)*x+C(7)),4);
forth_segment_EIv= vpa((25/6*x^3-250/2*x^2+C(4)*x+C(8)),4);
EI= (3.876*10^-9)^-1;

v=piecewise((0<=x)&&(x<2),first_segment_EIv/EI , (2<=x)&&(x<=5),second_segment_EIv/EI , (5<=x)&&(x<=7), third_segment_EIv/EI , (7<=x)&&(x<=10), forth_segment_EIv/EI );
%EIv=vpa(EIv,5)
fplot(v)

g = diff(v, x);
solve(g == 0, x);
max_deflection_location = vpa(ANS, 3);
max_deflection= subs(v,x,max_deflection_location);

Answer 1

[Walter Roberson]

C = linsolve( double(A), double(B));

You will get nan and inf results. This is because rank(A) is only 7 instead of 8.

Your 6th equation is inconsistent with the previous equations.