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How can I avoid 'and' in result? or any other way to solve

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Tarsem Singh Khalsa
Tarsem Singh Khalsa le 14 Avr 2018
Clôturé : MATLAB Answer Bot le 20 Août 2021
I'm writing a code for vibration of beam, the problem is that after derivation and substituting boundary values the result contains 'and' relation between two equation. It maybe due to the assumption, but it is necessary. Is there a way to avoid 'and' in this result?
BC: (for cantilever beam, beam length = 4m)
Y(x=0)=0
Y'(x=0)=0
Y''(x=4)=0
Y'''(x=4)=0
code:
Y=A*sin(b*x)+B*cos(b*x)+C*sinh(b*x)+D*cosh(b*x);
Yx=[1 0;1 0;0 1;0 1];
% Yx(i,j)=> i=n, (n-1)th derivative of Y
% j=1, at x=0; j=2, at x=Length of beam
assume(b>0);
t=0;
for i=1:4
for j=1:2
if Yx(i,j)==0
continue
end
t=t+1;
dY=diff(Y(x,b),x,(i-1));
F=simplify(expand(subs(dY,x,Yx(5,j))==0,'ArithmeticOnly',true));
c=symvar(F);
if or(size(c,2)==1,c(1)~='b')
d=1;
else
d=2;
end
if t==4;
assume(c(d)~=0)
Y=simplify(expand(F,'ArithmeticOnly',true));
else
G=solve(F,c(d));
Y(x,b)=subs(Y,c(d),G);
end
end
end
disp(Y);
The final result is like this:
Y = sin(4*b) + sinh(4*b) ~= 0 and cosh(4*b)^2 + 2*cos(4*b)*cosh(4*b) + 1 == sinh(4*b)^2
I'm using Matlab R2013a
  2 commentaires
Walter Roberson
Walter Roberson le 14 Avr 2018
You should be able to add an assume() that asserts the first relationship to be true and then it should simplify() out.
It does appear to be true for all positive b.
Tarsem Singh Khalsa
Tarsem Singh Khalsa le 15 Avr 2018
Thanx that worked perfectly.

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