empty sym: 0-by-1. please help me

2021 5 4
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更新时间：2021 5 4
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a=9.61;
b=0.16;
fc=2000*10^6;
c=300*10^6;
A= 10^(1/10)-10^(20/10);
B=(20*log10(4*pi*fc/c))+10^(20/10);
syms R real;
y=(A/(1+a*exp(-b*(atand(500/R)-a))))+20*log10(R/(cosd(atand(500/R))))+(B)-10^10==0
sol=solve(y,R)
This is my scropt. I want to solve this equation, But mine gives me an Empty sym: 0-by-1 error whenever I try to run it.
Please help me

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Star Strider
Star Strider 2021-5-4
Ran in:

1 个投票

Ran in:
a=9.61;
b=0.16;
fc=2000*10^6;
c=300*10^6;
A= 10^(1/10)-10^(20/10);
B=(20*log10(4*pi*fc/c))+10^(20/10)
B = 138.4624
syms R real;
y=(A/(1+a*exp(-b*(atand(500/R)-a))))+20*log10(R/(cosd(atand(500/R))))+(B)-10^10
y = 
yfcn = matlabFunction(y)
yfcn = function_handle with value:
@(R)(log(R.*sqrt(1.0./R.^2.*2.5e+5+1.0)).*2.0e+1)./log(1.0e+1)-9.874107458820583e+1./(exp((atan(5.0e+2./R).*(-1.44e+2./5.0))./pi+9.61e+2./6.25e+2).*(9.61e+2./1.0e+2)+1.0)-9.999999861537628e+9
Rv = linspace(-1E+4, 1E+4);
figure
plot(Rv,real(yfcn(Rv)))
grid
% ylim([min(ylim) 1])
figure
plot(Rv,imag(yfcn(Rv)), '-r', 'LineWidth',2)
grid
ylim([-5 max(ylim)])
There is no solution because the function never crosses 0 on either the real or imaginary axes!

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