Editing Approximation (section)

====LaTeX symbols====
Typical meanings of [[LaTeX]] symbols.
* <math> \approx </math> (<code>\approx</code>) : approximate equality, like <math> \pi \approx 3.14</math>.
* <math> \not\approx </math> (<code>\not\approx</code>) : inequality, despite any approximation (<math>1 \not\approx 2</math>).
* <math> \simeq </math> (<code>\simeq</code>) : function asymptotic equivalence, like <math> f(n) \simeq 3n^2 </math>. 
** Thus, <math> \pi \simeq 3.14 </math> is wrong under this definition, despite wide use.
* <math> \sim </math> (<code>\sim</code>) : function proportionality; the <math>f(n)</math> used in <code>\simeq</code> is <math> f(n) \sim n^2 </math>.
* <math> \cong </math> (<code>\cong</code>) : figure congruence, like <math> \Delta ABC \cong \Delta A'B'C' </math>.
* <math> \eqsim </math> (<code>\eqsim</code>) : equal up to a constant.
* <math>\lessapprox</math> (<code>\lessapprox</code>) and <math>\gtrapprox</math> (<code>\gtrapprox</code>) : either an inequality holds or approximate equality.