matlab 求方程组的解

发布网友 发布时间：2022-03-25 19:55

我来回答

共1个回答

热心网友 时间：2022-03-25 21:24

syms x y z a b c
[x,y,z]=solve('72.8*(1+cos(a))=2*(sqrt(x*21.8)+sqrt(25.5*y)+sqrt(25.5*z))','50.8*(1+cos(b))=2*sqrt(x*50.8)','48*(1+cos(c))=2*(sqrt(x*29)+sqrt(47*y)+sqrt(1.92*z))','x,y,z')
x =

12.700000000000000000000000000000+25.400000000000000000000000000000*cos(b)+12.700000000000000000000000000000*cos(b)^2

y =

-.984169311707206540241988580218*cos(c)+9.734398050752790240685157559*cos(a)*cos(b)-23.462398366292790782350185322144*cos(c)*cos(b)+7.14896766620738069752563394849*cos(b)^2+3.33416391624979691912915638814*cos(a)^2+.409581398297044880227538559881*cos(a)+.59974496762043211062439587258181*cos(b)-16.023090169105698668480172257920*cos(c)*cos(a)+19.250659611845600192713968847131*cos(c)^2+.12579480567470121256861223e-1

z =

.151945654385968269160012565125e-193*(.58477278352492431981436322974990e98+.58477278352492431981436322974990e98*cos(a)-.26731041191058757560106827855831e98*((cos(b)+1.)^2)^(1/2)-1.*(-.7711391078760381210034820223e194*cos(c)+.262081202967154457022801098613e195*cos(a)*cos(b)-.154413092372449407363127225476e196*cos(c)*cos(b)+.470490590306928474554525841306e195*cos(b)^2+.21943134403702282352778341593461e195*cos(a)^2+.82783874266682206962299704487537e192+.2695579848190730904101435319e194*cos(a)+.394710181113160404300458852655e194*cos(b)-.10545277016218098275353846992100e196*cos(c)*cos(a)+.12669437431192070703927236534687e196*cos(c)^2)^(1/2))^2

______________________________
就是代入求值就行了，例如：（接着上面的求X）
x=subs(x,{a,b,c},{77.7,33.3,48.5})

x =

127/10+127/5*cos(333/10)+127/10*cos(333/10)^2
__________________________________
其实在一开始就给定a,b,c的值也是可以的，如果不要求一定要求解析解的话，楼下说的fsolve倒也是一种选择