作业帮为什么用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
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.