我刚开始使用Python和Sympy,但在使用Sympy解决多元不等式时遇到问题。
假设我在文件中有很多这样的函数:
cst**(sqrt(x)/2)/cst
exp(sqrt(cst*x**(1/4)))
log(log(sqrt(cst + exp(x))))
(y**(1/4) + y)**cst
sqrt(y/log(x))/cst
sqrt(cst**log(cst) + x)
(y**2)**(x/4)
sqrt(y*sqrt(cst**y))
log(sqrt(2)*sqrt(cst)*x)
我需要对它们进行求导,设置常数的值并检查每个函数f是否
df/dx > 0
df/dy < 0
当 x 属于 [0, +oo),y 属于 [0, 1] 时。
为求导,我使用:
dx = diff(f, x)
dy = diff(f, y)
然后当我尝试:
cst = 2 #(for example)
solve(dx > 0)
我遇到了这个错误:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/local/lib/python2.7/dist-packages/sympy/solvers/solvers.py", line 634, in solve
symbols=symbols)
File "/usr/local/lib/python2.7/dist-packages/sympy/solvers/inequalities.py", line 374, in reduce_inequalities
raise NotImplementedError("only univariate inequalities are supported")
NotImplementedError: only univariate inequalities are supported
但是如果我尝试那样做:
x=Symbol('x', real=True, postive=True, nonzero=True)
y=Symbol('y', real=True, postive=True, nonzero=True)
solve(x**2+y > 0)
我得到了:
True
有哪种方法可以解决多元不等式并总是得到可行的答案?例如,我想要得到:
solve(x**2-y>0)
Or(x>-sqrt(y), x>sqrt(y))
哪种方法可以获得好的和可行的答案?是否有办法解决多元不等式?