[英]Simplifying exponential representation of hyperbolic functions in sympy
I am trying to rewrite some exponential functions in an expression to cosh and sinh. 我试图将表达式中的一些指数函数重写为cosh和sinh。 The rewrite() function works to get from a hyperbolic function to its exponential representation.
rewrite()函数用于从双曲函数到其指数表示。 But it does not work to get back.
但它无法回复。
>>> import sympy
>>> x=sympy.Symbol('x')
>>> sympy.cosh(x).rewrite(sympy.exp)
exp(x)/2 + exp(-x)/2
>>> sympy.cosh(x).rewrite(sympy.exp).rewrite(sympy.cosh)
exp(x)/2 + exp(-x)/2
I would expect the result of the last command to be 'cosh(x)'. 我希望最后一个命令的结果是'cosh(x)'。 Can someone explain to me why it is not?
有人可以向我解释为什么不是吗? I tried to find some documentation on the rewrite() function but the only bit I found was the short section in http://docs.sympy.org/latest/tutorial/simplification.html that is not really helpful.
我试图找到关于rewrite()函数的一些文档,但我找到的唯一一点是http://docs.sympy.org/latest/tutorial/simplification.html中的简短部分,这并不是很有用。
Applying .rewrite(sympy.cos)
returns cosh(x)
as you wanted. 应用
.rewrite(sympy.cos)
返回cosh(x)
。 Apparently, the hyperbolic cosine is treated by rewrite
as a variant of the normal one. 显然,双曲余弦值通过
rewrite
来处理,作为正常值的变体。
Here is a reference on rewrite method . 这是重写方法的参考 。
Alternatively, simplify(expr)
also transforms exp(x)/2 + exp(-x)/2
into cosh(x)
. 或者,
simplify(expr)
也将exp(x)/2 + exp(-x)/2
转换为cosh(x)
。
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