Question

你好朋友，我想弄清楚以下问题：假设，我们有表达式，

syms t k A0
r1=(-1+k-3/4*k*A0^2)*sin(t)+1/4*k*A0^2*sin(3*t)+A0*sin(5*t);

我们要移除sin(t)的系数，并为A0＆amp;最后把这个值放到表达式的其余部分。我们怎样才能完成它而不需要剪切和粘贴。

Answer 1

我不知道MATLAB版本5.3.1有哪些符号功能可用，但您可以使用当前的COEFFS，SUBS和SOLVE函数来解决问题Symbolic Math Toolbox：

>> eqCoeffs = coeffs(r1,sin(t));  %# Get coefficients for polynomial in sin(t)
>> b = eqCoeffs(2);               %# Second coefficient is what you want
>> bValue = 1;                    %# The value to set the coefficient equal to
>> newA0 = solve(subs('b = bValue'),A0)  %# Solve for A0

newA0 =

 -(2*3^(1/2)*(k - 2)^(1/2))/(3*k^(1/2))  %# Note there are two values since
  (2*3^(1/2)*(k - 2)^(1/2))/(3*k^(1/2))  %#   A0 is squared in the equation

>> r2 = subs(r1,A0,newA0)                %# Substitute the new A0 values into r1

r2 =

 sin(t) + (sin(3*t)*(k - 2))/3 - (2*3^(1/2)*sin(5*t)*(k - 2)^(1/2))/(3*k^(1/2))
 sin(t) + (sin(3*t)*(k - 2))/3 + (2*3^(1/2)*sin(5*t)*(k - 2)^(1/2))/(3*k^(1/2))

请注意，sin(t)这两个方程中r2的系数等于1（我用于bValue的值）。

我们如何在matlab ver 5.3.1中存储符号表达式的一些特定系数？

1 个答案: