Question

MATLAB solve解方程，已经赋值变量，结果仍然还有变量

syms PR1 Sp;
PR1=0.57;Sp=3;
[S1,Sd,Sdp]=solve('0.5744==log(1500)/(log(1500)+S1)','S1==Sdp+Sp','9==Sdp+3+Sd','S1','Sd','Sdp')

结果
S1 =
5.4187092561727581656058737313416
Sd =
Sp + 0.58129074382724183439412626865839
Sdp =
5.4187092561727581656058737313416 - 1.0*Sp

Answer 1

出在问题原因有：

1、声明变量错误，变量应该写所求的变量。正确的写法

syms S1 Sd Sdp;

2、 solve 命令函数 书写错误（多了单引号）。正确的写法

[S1,Sd,Sdp]=solve(0.5744==log(1500)/(log(1500)+S1),S1==Sdp+Sp,9==Sdp+3+Sd,'S1','Sd','Sdp')

运行下列代码

>>syms S1 Sd Sdp;
>>PR1=0.57;Sp=3;
>>[S1,Sd,Sdp]=solve(0.5744==log(1500)/(log(1500)+S1),S1==Sdp+Sp,9==Sdp+3+Sd,'S1','Sd','Sdp')

>> S1=vpa(S1,10)

>> Sd=vpa(Sd,10)

>> Sdp=vpa(Sdp,10)