\ddots{a} - LaTeX Symbol

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⋱ a

\ddots{a}

The \ddots command in LaTeX is used to produce diagonal ellipsis, which is a series of three dots arranged diagonally. This symbol is often used in mathematical expressions to indicate a continuation of a pattern or sequence, especially in matrices or series.

Examples

a_{11} a_{21} ⋮ a_{m 1} a_{12} a_{22} ⋮ a_{m 2} \dots \dots ⋱ \dots a_{1 n} a_{2 n} ⋮ a_{mn}

Indicating continuation in a matrix

\begin{bmatrix} a_{11} & a_{12} & \cdots & a_{1n} \\ a_{21} & a_{22} & \cdots & a_{2n} \\ \vdots & \vdots & \ddots & \vdots \\ a_{m1} & a_{m2} & \cdots & a_{mn} \end{bmatrix}

1 + q + q^{2} + ⋱

Representing an infinite series

1 + q + q^2 + \ddots

T = t_{11} t_{21} ⋮ t_{n 1} t_{12} t_{22} ⋮ t_{n 2} \dots \dots ⋱ \dots t_{1 n} t_{2 n} ⋮ t_{nn}

Diagonal ellipsis in a transformation matrix

T = \begin{bmatrix} t_{11} & t_{12} & \cdots & t_{1n} \\ t_{21} & t_{22} & \cdots & t_{2n} \\ \vdots & \vdots & \ddots & \vdots \\ t_{n1} & t_{n2} & \cdots & t_{nn} \end{bmatrix}