solve of equation system misses trivial simplifications

[rwst]

Some trivial substitutions are not done by solve:

sage: x,y=var('x,y')
sage: solve([y==exp(x),2*y-exp(x)==1],x,y)
[y == e^x, 2*y - e^x == 1]

and, as reported in http://ask.sagemath.org/question/23652/solve-equations-with-sinx/

sage: solve([y==sin(x),y+4*sin(x)==5],x,y)
[y == sin(x), y + 4*sin(x) == 5]

Component: calculus

Author: Akshay Ajagekar

Branch/Commit: u/ajagekar.akshay/Trac16753 @ 88dec5a

Issue created by migration from https://trac.sagemath.org/ticket/16753

[rwst]

comment:1

Set to critical because it makes Sage look really stupid.

[rwst]

Description changed:

--- 
+++ 
@@ -1,5 +1,3 @@
-(please write a better title)
-
 Some trivial substitutions are not done by solve:
 
 ```

[sagetrac-ajagekar-akshay]

comment:3

I think it is maxima which is unable to solve the equations and returns

%solve([y = sin(x), y + 4*sin(x) = 5],[x,y])

in this case. Sage converts this to list of solutions. Can we condition sage to return "Unable to solve" instead of returning the equations? while reporting this upstream.

[rwst]

comment:4

You mean a general change for unsolved equations/relations? That would be a different ticket which you would have to open. I'm not against a change but I'd rather have solve return a set, and in case of unsolved an empty set.

[sagetrac-ajagekar-akshay]

comment:5

A test which returned initial function instead of solutions was failing

solve([sin(x)==x,y^2==x],x,y)
Expected:
    [sin(x) == x, y^2 == x]
Got:
    []

I have changed that test. Please have a look.

[sagetrac-ajagekar-akshay]

Branch: u/ajagekar.akshay/Trac16753

[rwst]

comment:7

Your ticket branch shows MeatAxe changes. Probably you branched not from develop. Use git trac checkout to have a proper start.