fix: Improve formula presentation

[junyixu]

No description provided.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.57%. Comparing base (c310fb5) to head (27b4d09).
Report is 3 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #697   +/-   ##
=======================================
  Coverage   89.57%   89.57%           
=======================================
  Files          11       11           
  Lines         969      969           
=======================================
  Hits          868      868           
  Misses        101      101           

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[andreasnoack]

Would be good to show the before and after in a comment

[junyixu]

Before:

After:

[junyixu]

I'm not sure. Represent a function $f$ that maps an element $x$ in a set to another element $y$:
$$f: x \mapsto y.$$
But in the original doc page,

it seems the author intended to use \to to represent a type of change.

[mcabbott]

Sorry just went by your pictures, where after used it for two kinds of change. x to x_eps, and x_eps to f(x_eps). It seems the original commits the same sin, could fix that too?

[junyixu]

Sorry just went by your pictures, where after used it for two kinds of change. x to x_eps, and x_eps to f(x_eps). It seems the original commits the same sin, could fix that too?

I force-pushed a new commit. What do you think?

Before:

After: