# Command/startformula

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# \startformula

## Syntax

 \startformula ... \stopformula

## comment

Note: these are defined by the following lines in core-mat.tex:

\setvalue{\e!start\v!formula}{\dostartformula{}}
\setvalue{\e!stop \v!formula}{\dostopformula}

## Example

\starttext

This is the first mathematical formula \placeformula[First] \startformula

\sin^2(t)^2 + \cos^2(t) = 1.

\stopformula

This is another formula \placeformula[eqn:tangent] \startformula

\cos^2(t) = \frac{1}{1+\tan^2(t)}.

\stopformula As one may see from relation~(\in[eqn:tangent]), $\cos(t)$ and $\sin(t)$ can be determined by $\tan(t)$\dots

This is the third formula \placeformula[Pythagora] \startformula

|a+b|^2 = |a|^2 + |b|^2

\stopformula Clearly equality (\in[Pythagora]) holds for $a,b \in {\Bbb R}^n$ if and only if $(a|b) =0$, where the scalar product $(\cdot|\cdot)$ on ${\Bbb R}^n$ is defined to be \startformula

(a|b) := a\cdot b =\sum_{j=1}^{n}a_jb_j, \qquad |a|^2 := (a|a).

\stopformula (Note that the above equation is {\it not\/} numbered). \stoptext