I'm using sage to give me the inverse of functions using solve(). Most of the time, it works fine. But when I have roots of anything involved(for example, "solve((5x-2)^(1/7)==y,x)", I get the error message in the title. Is there any way around this?
Hi,
The ECL lib complains because (to its mind) the answer depends on the fact that y being positive negative or zero. To specify some restriction on variables within Sage just do
sage: var('y')
y
sage: assume(y > 0)
sage: solve((5*x-2)^(1/7)==y,x)
[x == 1/5*y^7 + 2/5]
Now, the operation x -> x^(1/7) looks unamiguous on RR because x -> x^7 is a bijection on RR.
An alternative would be to rewrite the equation
sage: var('y')
y
sage: solve((5*x-2)==y^7,x)
[x == 1/5*y^7 + 2/5]
Asked: 2013-10-20 10:22:35 +0100
Seen: 1,634 times
Last updated: Oct 20 '13
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