How to solve these two equations for 'tau' and 'b'? All the other symbols are constants. Please help??

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Anik Faisal 2018-8-7

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评论： Anik Faisal 2018-8-9

采纳的回答： Stephan

I've tried using the sysms command but not sure I'm getting the input formatting correct

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Stephan 2018-8-7

you should also show us what you have done so far by using syms...

Anik Faisal 2018-8-7

在 MATLAB Online 中打开

syms m b nu R rc tau g b0 u0
eqn1=(m*b/2)*((2-nu)/(1-nu))*R*log(R/rc)-tau*pi*R^2+(g*pi^2*R^2/b0)*sin(2*pi*(u0+b)/b0)==0;
eqn2=(m*b^2/4)*((2-nu)/(1-nu))*(1+log(R/rc))-2*pi*tau*R*b-g*pi*R*sin(pi*b/b0)*sin(pi*(2*u0+b)/b0)==0;
eqns=[eqn1 eqn2];
vars=[b tau];
[solv,solu]=solve(eqns,vars)

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采纳的回答

Stephan 2018-8-7

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在 MATLAB Online 中打开

Hi,

i used the isolate function instead of solve and found:

sol_tau =
tau == -(2778046668940015*R*g*sin((2*pi*(b + u0))/b0) + 281474976710656*b*b0*m*log(R/rc) - 2778046668940015*R*g*nu*sin((2*pi*(b + u0))/b0) - 140737488355328*b*b0*m*nu*log(R/rc))/(281474976710656*R*b0*pi*(nu - 1))
sol_b =
b == 0

by using these lines of code:

syms m b nu R rc tau g b0 u0
eqn1=(m*b/2)*((2-nu)/(1-nu))*R*log(R/rc)-tau*pi*R^2+(g*pi^2*R^2/b0)*sin(2*pi*(u0+b)/b0)==0;
eqn2=(m*b^2/4)*((2-nu)/(1-nu))*(1+log(R/rc))-2*pi*tau*R*b-g*pi*R*sin(pi*b/b0)*sin(pi*(2*u0+b)/b0)==0;
sol_tau = simplifyFraction(isolate(eqn1,tau))
eqn2_new = simplifyFraction(subs(eqn2,tau,rhs(sol_tau)));
sol_b = simplifyFraction(isolate(eqn2_new,b))

I did not check if you have typos in your equations...

Best regards

Stephan