为什么用matlab算这个会出现复数?>> syms x u;v=-19675*(x^2) + 5556.2*x - 109.75;q=-4.1973*x + 2.1639;cf=-0.0003*(v-u) + 0.0811;f=0.5*3.14*0.27*0.001*cf*q*(v-u)^2;res=int(f,x,0.05,0.18);b=vpa(res);solve(b-0.2)ans =42.309155108272078569729911
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![为什么用matlab算这个会出现复数?>> syms x u;v=-19675*(x^2) + 5556.2*x - 109.75;q=-4.1973*x + 2.1639;cf=-0.0003*(v-u) + 0.0811;f=0.5*3.14*0.27*0.001*cf*q*(v-u)^2;res=int(f,x,0.05,0.18);b=vpa(res);solve(b-0.2)ans =42.309155108272078569729911](/uploads/image/z/5164797-21-7.jpg?t=%E4%B8%BA%E4%BB%80%E4%B9%88%E7%94%A8matlab%E7%AE%97%E8%BF%99%E4%B8%AA%E4%BC%9A%E5%87%BA%E7%8E%B0%E5%A4%8D%E6%95%B0%3F%3E%3E+syms+x+u%3Bv%3D-19675%2A%28x%5E2%29+%2B+5556.2%2Ax+-+109.75%3Bq%3D-4.1973%2Ax+%2B+2.1639%3Bcf%3D-0.0003%2A%28v-u%29+%2B+0.0811%3Bf%3D0.5%2A3.14%2A0.27%2A0.001%2Acf%2Aq%2A%28v-u%29%5E2%3Bres%3Dint%28f%2Cx%2C0.05%2C0.18%29%3Bb%3Dvpa%28res%29%3Bsolve%28b-0.2%29ans+%3D42.309155108272078569729911)
为什么用matlab算这个会出现复数?>> syms x u;v=-19675*(x^2) + 5556.2*x - 109.75;q=-4.1973*x + 2.1639;cf=-0.0003*(v-u) + 0.0811;f=0.5*3.14*0.27*0.001*cf*q*(v-u)^2;res=int(f,x,0.05,0.18);b=vpa(res);solve(b-0.2)ans =42.309155108272078569729911
为什么用matlab算这个会出现复数?
>> syms x u;
v=-19675*(x^2) + 5556.2*x - 109.75;
q=-4.1973*x + 2.1639;
cf=-0.0003*(v-u) + 0.0811;
f=0.5*3.14*0.27*0.001*cf*q*(v-u)^2;
res=int(f,x,0.05,0.18);
b=vpa(res);
solve(b-0.2)
ans =
42.309155108272078569729911709729-125.11218219192134613585563974728*i
42.309155108272078569729911709729+125.11218219192134613585563974728*i
358.08028292832080771770708102234
为什么用matlab算这个会出现复数?>> syms x u;v=-19675*(x^2) + 5556.2*x - 109.75;q=-4.1973*x + 2.1639;cf=-0.0003*(v-u) + 0.0811;f=0.5*3.14*0.27*0.001*cf*q*(v-u)^2;res=int(f,x,0.05,0.18);b=vpa(res);solve(b-0.2)ans =42.309155108272078569729911
你先看一下你的b
它是一个三次多项式.
理论上它有三个根.
要不然就是三个实根,
要不然就是一个实根和两个共轭的复根.
结果应当没有问题.