Problem with equations solver

2018 7 18
1 个回答
更新时间：2018 8 2
3 次查看（30 天）

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Hi all, I've got a problem with the equations solver. I'm sure that my code is wrong (in the function "solve") because I've used symbolic functions, but I don't know where is the mistake.
e
syms alpha(t) beta(t) c(t)
eqns = [(a*cos(alpha))+(b*cos(beta))==0 , (a*sin(alpha))+(b*sin(beta))==c];
sol = solve(eqns, [c, beta]);
ALPHA=0:pi/100:4*pi;
plot(ALPHA, subs(sol.c(2,1), alpha(t) ,ALPHA))
eqns_dot=diff(eqns, t)

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回答（1 个）

0 个投票

Hi Carlo,
I understand that you are having issues when using the 'solve' function to solve symbolic equations.
When solving symbolic equations using 'solve(eqn,vars)', 'vars' should be an array of symbolic variables and not symbolic functions. Moreover when using 'plot(x,y)', 'x' and 'y' must be numeric, datetime, duration or an array convertible to double. Here I assume a = 2 and b = 3 and substitute these in sol.c when plotting.
syms a b c alpha(t) beta
eqns = [(a*cos(alpha))+(b*cos(beta))==0 , (a*sin(alpha))+(b*sin(beta))==c];
sol = solve(eqns, [c, beta]);
ALPHA=0:pi/100:4*pi;
plot(ALPHA, subs(sol.c(2,1), {alpha(t) ,a,b},{ALPHA,2,3}));
eqns_dot=diff(eqns, t);

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