Sympy 解方程

1. 解普通方程

   from sympy import *x = Symbol('x')y = Symbol('y')print solve([2 * x - y - 3, 3 * x + y - 7],[x, y])

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2. 解微积分
   

   from sympy import *n = Symbol('n')s = ((n+3)/(n+2))**n#无穷为两个小写oprint limit(s, x, oo)

3. 求定积分
   

   from sympy import *t = Symbol('t')x = Symbol('x')m = integrate(sin(t)/(pi-t),(t,0,x))n = integrate(m,(x,0,pi))print n

   

4. 解微分方程

   #y' = 2xy  的通解from sympy import *f = Function('f')x = Symbol('x')print dsolve(diff(f(x),x) - 2*f(x)*x,f(x))#说明：f = Function('f')x = Symbol('x')#表示f(x)的导：diff(f(x), x, index)    >>> diff(sin(x), x, 1)cos(x)dsolve(eq, f(x))    #第一个参数为微分方程（要先将等式移项为右端为0的形式)    #第二个参数为要解的函数(在微分方程中)

5. 矩阵化简

   

   from sympy import *x1,x2,x3 = symbols('x1 x2 x3')a11,a12,a13,a22,a23,a33 = symbols('a11 a12 a13 a22 a23 a33')m = Matrix([[x1,x2,x3]])n = Matrix([[a11,a12,a13],[a12,a22,a23],[a13,a23,a33]])v = Matrix([[x1],[x2],[x3]])f = m * n * vf[0] 化简， subs代入计算print f[0].subs({x1:1, x2:1, x3:1})