tikz.dev / tkz-euclide Manual

tkz-euclide

Marking and labelling

32 Labelling points

32.1 Label for a point: \tkzLabelPoint

You can add several labels to the same point by using this macro several times.

  • \tkzLabelPoint[⟨local options⟩](⟨point⟩)⟨label⟩

    • argumentsexample
    point\tkzLabelPoint(A){$A_1$}
    optionsdefaultdefinition
    TikZ optionscolor, position etc.

    Optionally, you can use any TikZ style, in particular placements such as above, right, …

32.1.1 Example with \tkzLabelPoint

Compiled output

\begin{tikzpicture}
\tkzDefPoint(0,0){A}
\tkzDefPoint(4,0){B}
\tkzDefPoint(0,3){C}
\tkzDrawSegments(A,B B,C C,A)
\tkzDrawPoints(A,B,C)
\tkzLabelPoint[left,red](A){$A$}
\tkzLabelPoint[right,blue](B){$B$}
\tkzLabelPoint[above,purple](C){$C$}
\end{tikzpicture}
32.1.2 Label and reference

The reference of a point is what lets you use the point in the code; the label is the name of the point that is displayed.

Compiled output

\begin{tikzpicture}
\tkzDefPoint(2,0){A}
\tkzDrawPoint(A)
\tkzLabelPoint[above](A){$A_1$}
\end{tikzpicture}
32.2 Add labels to points \tkzLabelPoints

You can quickly place several labels when the references of the points are identical to the labels and when all the labels are placed in the same way relative to their points. By default, below right is used.

  • \tkzLabelPoints[⟨local options⟩](⟨\(A_1,A_2,...\)⟩)

    • argumentsexampleresult
    list of points\tkzLabelPoints(A,B,C)Display of \(A\), \(B\) and \(C\)

    This macro reduces the number of lines of code, but all the points rarely need the same label position.

32.2.1 Example with \tkzLabelPoints

Compiled output

\begin{tikzpicture}
\tkzDefPoint(2,3){A}
\tkzDefShiftPoint[A](30:2){B}
\tkzDefShiftPoint[A](30:5){C}
\tkzDrawPoints(A,B,C)
\tkzLabelPoints(A,B,C)
\end{tikzpicture}
32.3 Automatic position of labels \tkzAutoLabelPoints

The label of a point is placed in the direction defined by a center, given with the option center, and the point. The distance between the label and the point is a percentage of the distance between the center and the point, given by dist.

  • \tkzAutoLabelPoints[⟨local options⟩](⟨\(A_1,A_2,...\)⟩)

    • argumentsexampleresult
    list of points\tkzAutoLabelPoint(A,B,C)Display of \(A\), \(B\) and \(C\)
32.3.1 Label for points with \tkzAutoLabelPoints

Here the labels are positioned relative to the centroid of \(A\), \(B\), \(C\) and \(O\).

Compiled output

\begin{tikzpicture}[scale=1]
\tkzDefPoint(2,1){O}
\tkzDefRandPointOn[circle=center O radius 1.5]\tkzGetPoint{A}
\tkzDefPointBy[rotation=center O angle 100](A)\tkzGetPoint{C}
\tkzDefPointBy[rotation=center O angle 78](A)\tkzGetPoint{B}
\tkzDrawCircle(O,A)
\tkzDrawPoints(O,A,B,C)
\tkzDrawSegments(C,B B,A A,O O,C)
\tkzDefTriangleCenter[centroid](A,B,C) \tkzGetPoint{G}
\tkzDrawPoint(tkzPointResult)
\tkzAutoLabelPoints[center=G,dist=.5](O,A,B,C)
\end{tikzpicture}

33 Labelling segments

33.1 The macros \tkzLabelSegment and \tkzLabelSegments

  • \tkzLabelSegment[⟨local options⟩](⟨pt1,pt2⟩){⟨label⟩}

    • This macro places a label along a segment or a line. The options are those of TikZ, for example pos.

    argumentexampledefinition
    label\tkzLabelSegment(A,B){\(5\)}label text
    (pt1,pt2)(A,B)label along \([AB]\)
    optionsdefaultdefinition
    pos.5label’s position
33.1.1 Labels above and below a segment

Compiled output

\begin{tikzpicture}
\tkzDefPoint(0,0){A}
\tkzDefPoint(6,0){B}
\tkzDrawSegment(A,B)
\tkzLabelSegment[above,pos=.8](A,B){$a$}
\tkzLabelSegment[below,pos=.2](A,B){$4$}
\end{tikzpicture}
33.1.2 Example: blackboard

Compiled output

\tikzstyle{background rectangle}=[fill=black]
\begin{tikzpicture}[show background rectangle,scale=.4]
\tkzDefPoint(0,0){O}
\tkzDefPoint(1,0){I}
\tkzDefPoint(10,0){A}
\tkzDefPointWith[orthogonal normed,K=4](I,A)
\tkzGetPoint{H}
\tkzDefMidPoint(O,A) \tkzGetPoint{M}
\tkzInterLC(I,H)(M,A)\tkzGetPoints{B}{C}
\tkzDrawSegments[color=white,line width=1pt](I,H O,A)
\tkzDrawPoints[color=white](O,I,A,B,M)
\tkzMarkRightAngle[color=white,line width=1pt](A,I,B)
\tkzDrawArc[color=white,line width=1pt,
style=dashed](M,A)(O)
\tkzLabelSegment[white,right=1ex,pos=.5](I,B){$\sqrt{a}$}
\tkzLabelSegment[white,below=1ex,pos=.5](O,I){$1$}
\tkzLabelSegment[pos=.6,white,below=1ex](I,A){$a$}
\end{tikzpicture}
33.1.3 Labels and option swap

Compiled output

\begin{tikzpicture}[rotate=-60]
\tkzSetUpStyle[red,auto]{label style}
\tkzDefPoint(0,1){A}
\tkzDefPoint(2,4){C}
\tkzDefPointWith[orthogonal normed,K=7](C,A)
\tkzGetPoint{B}
\tkzDefSpcTriangle[orthic](A,B,C){N,O,P}
\tkzDefTriangleCenter[circum](A,B,C)
\tkzGetPoint{O}
\tkzDrawPolygon[green!60!black](A,B,C)
\tkzDrawLine[dashed,color=magenta](C,P)
\tkzLabelSegment(B,A){$c$}
\tkzLabelSegment[swap](B,C){$a$}
\tkzLabelSegment[swap](C,A){$b$}
\tkzMarkAngles[size=1,
color=cyan,mark=|](C,B,A A,C,P)
\tkzMarkAngle[size=0.75,
color=orange,mark=||](P,C,B)
\tkzMarkAngle[size=0.75,
color=orange,mark=||](B,A,C)
\tkzMarkRightAngles[german](A,C,B B,P,C)
\tkzAutoLabelPoints[center = O,dist= .1](A,B,C)
\tkzLabelPoint[below left](P){$P$}
\end{tikzpicture}

  • \tkzLabelSegments[⟨local options⟩](⟨pt1,pt2 pt3,pt4 ...⟩)

    • The arguments are a list of pairs of points. The TikZ styles are available.

33.1.4 Labels for an isosceles triangle

Compiled output

\begin{tikzpicture}[scale=1]
\tkzDefPoints{0/0/O,2/2/A,4/0/B,6/2/C}
\tkzDrawSegments(O,A A,B)
\tkzDrawPoints(O,A,B)
\tkzDrawLine(O,B)
\tkzLabelSegments[color=red,above=4pt](O,A A,B){$a$}
\end{tikzpicture}

34 Labelling lines

34.1 The macro \tkzLabelLine

  • \tkzLabelLine[⟨local options⟩](⟨pt1,pt2⟩){⟨label⟩}

    • argumentsdefaultdefinition
    label\tkzLabelLine(A,B){$\Delta$}
    optionsdefaultdefinition
    pos.5pos is an option for TikZ, but essential in this case…

    As options, in addition to pos, you can use all the TikZ styles, in particular placements such as above, right, …

34.1.1 Example with \tkzLabelLine

An important option is pos: it places the label along the line. The value of pos can be greater than 1 or negative.

Compiled output

\begin{tikzpicture}
\tkzDefPoints{0/0/A,3/0/B,1/1/C}
\tkzDefLine[perpendicular=through C,K=-1](A,B)
\tkzGetPoint{c}
\tkzDrawLines(A,B C,c)
\tkzLabelLine[pos=1.25,blue,right](C,c){$(\delta)$}
\tkzLabelLine[pos=-0.25,red,left](C,c){again $(\delta)$}
\end{tikzpicture}

35 Labelling angles

35.1 The macros \tkzLabelAngle and \tkzLabelAngles

  • \tkzLabelAngle[⟨local options⟩](⟨A,O,B⟩)

    • There is only one option, dist (with or without unit), which can be replaced by the TikZ option pos (without unit). By default, the value is in centimeters.

    optionsdefaultdefinition
    pos1or dist, controls the distance from the top to the label.

    You can move the label with all the TikZ options: rotate, shift, below, etc.

35.1.1 Example by J. S. Bibra (.SE)

Compiled output

\begin{tikzpicture}[scale=.75]
\tkzDefPoint(0,0){C}
\tkzDefPoint(20:9){B}
\tkzDefPoint(80:5){A}
\tkzDefPointsBy[projection=onto B--C](A){a}
\tkzDrawPolygon[thick,fill=yellow!15](A,B,C)
\tkzDrawSegment[dashed, red](A,a)
\tkzDrawSegment[style=red, dashed,
dim={$10$,15pt,midway,font=\scriptsize,
rotate=90}](A,a)
\tkzMarkAngle(B,C,A)
\tkzMarkRightAngle(A,a,C)
\tkzMarkRightAngle(C,A,B)
\tkzFillAngle[fill=blue!20, opacity=0.5](B,C,A)
\tkzFillAngle[fill=red!20, opacity=0.5](A,B,C)
\tkzLabelAngle[pos=1.25](A,B,C){$\beta$}
\tkzLabelAngle[pos=1.25](B,C,A){$\alpha$}
\tkzMarkAngle(A,B,C)
\tkzDrawPoints(A,B,C)
\tkzLabelPoints(B,C)
\tkzLabelPoints[above](A)
\end{tikzpicture}
35.1.2 With pos

Compiled output

\begin{tikzpicture}[scale=.75]
\tkzDefPoints{0/0/O,5/0/A,3/4/B}
\tkzMarkAngle[size = 4,mark = ||,
arc=ll,color = red](A,O,B)%
\tkzDrawLines(O,A O,B)
\tkzDrawPoints(O,A,B)
\tkzLabelAngle[pos=2,draw,circle,
fill=blue!10](A,O,B){$\alpha$}
\end{tikzpicture}
35.1.3 pos and \tkzLabelAngles

Compiled output

\begin{tikzpicture}[rotate=30]
\tkzDefPoint(2,1){S}
\tkzDefPoint(7,3){T}
\tkzDefPointBy[rotation=center S angle 60](T)
\tkzGetPoint{P}
\tkzDefLine[bisector,normed](T,S,P)
\tkzGetPoint{s}
\tkzDrawPoints(S,T,P)
\tkzDrawPolygon[color=blue](S,T,P)
\tkzDrawLine[dashed,color=blue,add=0 and 3](S,s)
\tkzLabelPoint[above right](P){$P$}
\tkzLabelPoints(S,T)
\tkzMarkAngle[size = 1.8,mark = |,arc=ll,
color = blue](T,S,P)
\tkzMarkAngle[size = 2.1,mark = |,arc=l,
color = blue](T,S,s)
\tkzMarkAngle[size = 2.3,mark = |,arc=l,
color = blue](s,S,P)
\tkzLabelAngle[pos = 1.5](T,S,P){$60^{\circ}$}%
\tkzLabelAngles[pos = 2.7](T,S,s s,S,P){%
$30^{\circ}$}%
\end{tikzpicture}

  • \tkzLabelAngles[⟨local options⟩](⟨A,O,B⟩)(⟨A’,O’,B’⟩)etc.

    • With common options, there is a macro for several angles.

Finally, we need to give a label to a circle. Several methods are possible; here we look at \tkzLabelCircle.

36 Labelling circles

36.1 The macro \tkzLabelCircle

  • \tkzLabelCircle[⟨tikz options⟩](⟨O,A⟩)(⟨angle⟩){⟨label⟩}

    • optionsdefaultdefinition
    tikz optionscircle \(O\) center through \(A\)

    The TikZ styles can be used. The label is created, so it is passed between braces.

36.1.1 Labels around a circle

Compiled output

\begin{tikzpicture}
\tkzDefPoint(0,0){O} \tkzDefPoint(2,0){N}
\tkzDefPointBy[rotation=center O angle 50](N)
\tkzGetPoint{M}
\tkzDefPointBy[rotation=center O angle -20](N)
\tkzGetPoint{P}
\tkzDefPointBy[rotation=center O angle 125](N)
\tkzGetPoint{P'}
\tkzLabelCircle[above=4pt](O,N)(120){$\mathcal{C}$}
\tkzDrawCircle(O,M)
\tkzFillCircle[color=blue!10,opacity=.4](O,M)
\tkzLabelCircle[draw,
text width=2cm,text centered,left=24pt](O,M)(-120)%
{The circle\\ $\mathcal{C}$}
\tkzDrawPoints(M,P)\tkzLabelPoints[right](M,P)
\end{tikzpicture}

37 Labelling arcs

37.1 The macro \tkzLabelArc

  • \tkzLabelArc[⟨local options⟩](⟨pt1,pt2,pt3⟩){⟨label⟩}

    • This macro places a label along an arc. The options are those of TikZ, for example pos.

    argumentexampledefinition
    label\tkzLabelArc(A,B){\(5\)}label text
    (pt1,pt2,pt3)(O,A,B)label along the arc \(\widearc{AB}\)
    optionsdefaultdefinition
    pos.5label’s position
37.1.1 Label on arc

Compiled output

\begin{tikzpicture}
\tkzDefPoint(0,0){O}
\pgfmathsetmacro\r{2}
\tkzDefPoint(30:\r){A}
\tkzDefPoint(85:\r){B}
\tkzDrawCircle(O,A)
\tkzDrawPoints(B,A,O)
\tkzLabelArc[right=2pt](O,A,B){$\widearc{AB}$}
\tkzLabelPoints(A,B,O)
\end{tikzpicture}