Mathematics and chemistry (LaTeX)

Formulas (LaTeX)

Math (LaTeX). $E = mc^2$ in the middle of a sentence and $$…$$ as a block become a drawn formula in reading mode, in the exported file and in Ask your notes answers. The drawing follows the note theme. In formatted editing a block formula is drawn too, with the block bar on top (edit, copy, delete); and so is a formula in the middle of a sentence, seated on the text line. To edit it, double-click it or press Ctrl+Enter: it opens in the same bar. And Backspace right after it turns it back into $…$, to edit in place. In the text editor everything stays text: press Ctrl+E to see the formula. To get started, use Insert → Formula (LaTeX) in the note toolbar. Formulas are drawn with the system math font — on Windows, Cambria Math — rather than with the note's body font: that is where the math italics come from, along with the symbols a text font does not have and the parentheses and roots that grow with their content. With no math font installed, LightNote falls back to the note's font and draws those signs itself.

The subset covers Greek letters, operators and relations, the ^ exponent and the _ index, \frac, \sqrt (with index), \left…\right with growing delimiters, \sum/\prod/\int with limits, roman functions (\sin, \log…), \text/\mathrm/\mathbf/\mathbb the \mathcal/\mathfrak/\mathsf/\mathtt/\boldsymbol alphabets, \binom, \overset/\underset, \bmod/\pmod, the \big…\Bigg family the spaces \,/\quad/\hspace, the environments cases, matrix/pmatrix/bmatrix/vmatrix, aligned, gathered and array (with | and \hline), \overbrace/\underbrace, \begin{CD} and \begin{tikzcd} (commutative diagrams), \xrightarrow, \boxed/\cancel, \not, \substack, \|/\middle, \smash, \textcolor/\color (your hue; the lightness adjusts to the note's theme), \colorbox/\fcolorbox (the background comes out in the color you wrote, and the text adjusts to it), \tag (the equation label, right after it; in an align, one per row, lined up in a column), \phantom, \displaystyle and the infix forms \over/\atop/\choose. Coverage goes beyond this list: the comparison variants (\leqslant), logic (\land, \vDash), statistics operators (\argmax), the stretchy double arrows (\xRightarrow) and double brackets (\llbracket) are in too. The old TeX font switches also work — {\rm d}x, {\bf A}, {\cal L} — as does Dirac notation (\braket{\phi|\psi}). Macros defined in the formula itself (\newcommand, \def) last until its end, Unicode symbols typed directly (x ∈ ℝ) count as their commands, \text{…} accepts math between $…$, and a standalone formula can span several lines with \\. \label{eq:name} inside a $$ block numbers the equation in reading mode, with the same counter as {#eq:name}, and \eqref{eq:name} in the text becomes the number in parentheses. The LaTeX spelling works too: \(…\) inline and \[…\] as a block draw the same — it is the form ChatGPT usually emits. Whatever it cannot draw keeps showing up as the text you wrote.

Commutative diagrams with diagonal arrows (\begin{tikzcd}). \begin{CD} only draws horizontal and vertical arrows; the commutative triangle — the most common diagram there is — needs the diagonal. Each object is a cell (& separates them, \\ starts a row) and arrows are written inside the cell: A \arrow[r, "f"] \arrow[rd, "g"'] & B. The direction is a run of r/l/u/d (rd is the diagonal, rr spans two columns), and \ar and the shorthands (\rar, \dar, \drar) are the same arrow. The quoted label sits above an arrow going right; ' (or swap) puts it on the other side, which is what says whether the name falls inside or outside the figure. hook (inclusion), two heads (surjection), dashed, Rightarrow and equal work too. Curving (bend left) and any option this subset does not draw are refused with the name — drawing two curved arrows as straight ones would lay them on top of each other, claiming there is only one.

A $ in prose does not become a formula: in costs $5 and $10 the price stays a price, because the opening cannot be followed by a space nor the closing be preceded by one nor followed by a letter (that is what keeps PATH=$dir1:$dir2 from becoming a formula) — and $x$ between backticks stays code. When the formula does not appear, LightNote says why: a line below the $$ block, and only once per distinct message when the formula sits inside the text, naming the command or the delimiter it could not read. If the formula was pasted in the \(…\) spelling and you prefer $…$, Format → Normalize formulas to $ rewrites the selection (or the whole note) — in the text editor, which is where the note's characters are on screen.

Chemistry: mhchem and SMILES

Chemistry. The mhchem notation is drawn as well: \ce{2 H2 + O2 -> 2 H2O} places the subscripts on its own, -> and <=> become arrows (labelled with ->[\Delta]), Na+ and SO4^2- become charges, (aq) and (l) come out upright and tight, ^{227}_{90}Th lines up the isotope, and v/^ mark a precipitate and a released gas. \pu{123 kJ//mol} writes a quantity with its unit — the double slash becomes a fraction. The shifted equilibrium (<=>> and <<=>) draws the long arrow in the direction the reaction favors, spelled-out bonds (\bond{~}, \bond{~-}, \bond{...}) overlap their strokes the way textbooks do, and Kröger–Vink notation (O''_{i,x}, Li^x_{Li}) puts the effective charge in the superscript. Variables come out italic and elements upright: in NO_x the x is a variable, in Fe^{II} the II is the oxidation state.

Structures in LaTeX (\chemfig). \ce writes the formula; \chemfig{...} draws the skeleton inside the formula itself — \chemfig{H_3C-[:30]CH_2-[:-30]OH} is ethanol, \chemfig{*6(-=-=-=)} is benzene. The angle is yours: [:30] is absolute, [::45] is relative to the previous bond, and [3] counts eighths of a turn. Bonds are -, = and ~, and the stereochemistry wedges are >, <, >:, <:, >| and <| — the narrow tip sits at the stereocentre. Parentheses hang a branch and *6(...) closes a regular ring (**6(...) draws the aromatic circle); from a ring vertex, a bond with no written angle points outwards. Element symbols come out upright, and the line stops before the letter. chemfig’s departure and arrival nodes ([,,1,2]) are refused with the reason: they choose which part of the label the bond attaches to, and ignoring them would draw a different structure. A fused ring goes inside the first ring's body, right after the bond they share, and the inner one writes one bond fewer — that side is already drawn: naphthalene is \chemfig{*6(-=-*6(-=-=-)=-=)}.

Chemical structure (SMILES). A ```smiles fence with one SMILES line (CC(=O)Oc1ccccc1C(=O)O) is drawn as a skeletal formula in reading mode, in formatted editing, in the exported file and in Ask the notes answers. It is the counterpart of \ce: that one writes the formula, this one draws the molecule. The skeletal convention holds — carbon is not written (it is the vertex), the heteroatom gets its symbol in the theme accent, and the aromatic ring (c1ccccc1) gets the dashed circle inside. Stereochemistry is drawn: [C@H] and [C@@H] become a wedge — solid when the bond comes toward you, hashed when it goes back, with the narrow end at the stereocenter — and F/C=C/F and F/C=C\F come out trans and cis as written. What has no representation on paper (the named non-tetrahedral forms, such as @SP1) is accepted, and a caption inside the image says it was declared and not drawn. One fence draws one structure: a space in the middle of the line is refused, because in SMILES it ends the structure. When it cannot be read, LightNote says what is wrong (the bracket, the ring number, the element) and the code block stays as you wrote it. To start, use Insert → Structure (SMILES) on the note bar.