Uncommon notation for HTML

@http://blog.goo.ne.jp/ep58-kit/e/b38666b5d682c46b2672ec2cbdaef1fa
=Uncommon notation for HTML
/

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%0:Uncommon notation for HTML
http://blog.goo.ne.jp/bonsai-chat/e/1639d1d6a6d5d15519068eaacaf8434a
・[G8E%0:gooブログでの HTML 対策]
[G8E]:Prefix of File(made on 2016-08-14), [%1]:Prefix of Paragraph

In order to distinguish mathematical operator ’<’ from the leftmost char of HTML tags,  uncommon escape sequences are defined, as follows. 
%1:最も基本的なエスケープシーケンスは「`＜□＞」である．
・「□」は背景色が黄色の任意の文字列．
%11: エスケープシーケンスが開始，終了する（下付き，上付きでない）文字の背景色をシアンにする．
「`rθ(r,θ)₂=`xy(r*cos(θ),r*sin(θ))<sub>2</sub>」
「`rθφ(r,θ,φ)₃=(`xyz(rsinθcosφ,rsinθsinφ,rcosθ)<sub>3</sub>」
「`A[i]₃[j]³」
 %2:エスケープシーケンスは「`」で始まり，終了する文字（背景色はシアン）は構文によって異なる[G6J%2]．

%1:Document Example
[%2].[HCM:まず覚える数学公式]
・http://blog.goo.ne.jp/bonsai-chat/e/a5076adf63b2454047d625ab552b71f5

[%2031].[%2].[MATH.PDF]
実数「a」「b」の対「`(a,b)<sub>2</sub>」に対応させたxy平面上の点を「`xy(a,b)」で表わす．
・「xy平面」上の点「`xy(x,0)<sub>2</sub>」の集合（x軸）は数直線である．
・「`xy(a,b)₂」の背景色の意味は[G8E%11]参照．

%2:Remarks
The reason why uncommon notation is used is as follows using「＜」
・「＜」(JIS) is quite different from「<」 (ASCII)
%21:Even if 「＜」is expressed as「＆ｌｔ」, 「＆ｌｔ」becomes「＜」by saving a sentence after edition.
%22:Although TeX has Excellent notation, it is much easier to write using Wiki than using TeX,  typical examples are

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[%3].[?HCD:減加法の筆算]
(3):「0＋8＋6=14」,「1＋7＋5=13」,「1＋6＋5=12」.

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・Direct copy and paste instead of 「□_k」
[%0].[Puzzle1]
「□₁□₂□₃□₄×□₅＝□₆□₇□₈□₉」(No「□＜sub＞k＜/sub＞」)

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%3:Remarks on [%1]
%31:Switching the editors is waste of time, although existing Wiki editors are available to change background color, to use copy and paste, etc.
%311:Notation will be much advanced by people, developping  MathML, TeX to HTML, etc.
%32:Proportional font is not suitable to show values of cells on worksheet, and source program, etc.
%33:Using「\」is confusing, when one want to cite documents using 「\」
%331:{abc}(terminal) is not easy to recognize compared with 「abc」(JIS)

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={List of Files}