“Find the exterior angle of a heptagon.”
this is the question
the result it gave me is 231.429 degrees
but i this is not the angle i want
this the angle i want in this link : Heptagon - math word definition - Math Open Reference
help me please how to use wolfram alpha
thank you 
Hmmm. That’s strange. I wouldn’t have called what you linked “the exterior angle of a regular heptagon”. I’m not sure what I would call it exactly.
But it is clear that the value you’re looking for is related to exterior and interior angle by a simple formula:
(angle you’re looking for) + (interior angle) + (angle you’re looking for) = (exterior angle)
I probably would have called the angle you’re looking something like the “tangent angle”, which seems to be a term used by others as well. A little of bit geometry also shows that the angle you’re looking for is really just the “central angle” of the polygon, which you can get by searching “central angle of a regular heptagon”.