Empty space under a figure

Question

I am getting a significant amount of empty space under the following figure. How do I get rid of it? (I am a new user and I don't know how to post a tex code.)

\documentclass{article}

\usepackage{amsmath}
\usepackage{tikz}
\usepackage{tkz-euclide}
\usetkzobj{all}

\begin{document}

\begin{figure}[h!]
\centering

    \begin{tikzpicture}
    \tkzDefPoint(0,0){A}
    \tkzDefPoint(5,0){B}
    \tkzLabelPoints[below](A)
    \tkzLabelPoints[below](B)
    \tkzDrawSegment(A,B)
    \tkzDefPoint(2,3){C}
    \tkzLabelPoints[above](C)
    \tkzDrawSegment(A,C)
    \tkzDrawSegment(B,C)
    \tkzDrawBisector(C,B,A)(P)
    \tkzDrawBisector(C,A,B)(Q)
    \tkzDrawBisector(A,C,B)(R)
    \tkzDefCircle[in](A,B,C)\tkzGetPoint{I}\tkzGetLength{rIN}
    \tkzDrawCircle[R](I,\rIN pt)

    \draw[red] (I) -- ($(A)!(I)!(C)$)++(-30:0.1) -- ++(56:0.1) -- +(-34:-0.1);
    \draw[red] (I) -- ($(A)!(I)!(B)$) ++(90:0.1) -- ++(0:-0.1) -- +(-90:0.1);
    \draw[red] (I) -- ($(B)!(I)!(C)$) ++(45:-0.1) -- ++(-45:0.1) -- +(45:0.1);
    \draw (I)+(.2,-.3) node {$I$};
    \end{tikzpicture}
    \caption{Inscribed circle.}    
    \end{figure}  

\end{document}

Answer 1

The problem is, as cfr mentions in her answer, that in calculating some elements (in your case, the bisectors and even the inscribed circle) the bounding box gets enlarged. ANother way to prevent the problem, instead of interrupting the bounding box, is to use the native \tkzClip command.

Notice also that instead of manual \draws for the heights you can use

    \tkzDrawAltitude
    \tkzMarkRightAngle

as I did in my code. The complete code:

\documentclass{article}

\usepackage{amsmath}
\usepackage{tikz}
\usepackage{tkz-euclide}
\usetkzobj{all}

\begin{document}

\begin{figure}[h!]
\centering
    \begin{tikzpicture}
    \tkzInit[xmin=-0.3,xmax=5.3,ymin=-0.5,ymax=3.5]
    \tkzClip    
    \tkzDefPoint(0,0){A}
    \tkzDefPoint(5,0){B}
    \tkzLabelPoints[below](A)
    \tkzLabelPoints[below](B)
    \tkzDrawSegment(A,B)
    \tkzDefPoint(2,3){C}
    \tkzLabelPoints[above](C)
    \tkzDrawSegment(A,C)
    \tkzDrawSegment(B,C)
    \tkzDrawBisector(C,B,A)(P)
    \tkzDrawBisector(C,A,B)(Q)
    \tkzDrawBisector(A,C,B)(R)
    \tkzDefCircle[in](A,B,C)\tkzGetPoint{I}\tkzGetLength{rIN}
    \tkzDrawCircle[R](I,\rIN pt)
    \tkzSetUpLine[color=red]
    \tkzDrawAltitude(A,B)(I)
    \tkzMarkRightAngle[color=red,size=.15](I,tkzPointResult,A)
    \tkzDrawAltitude(B,C)(I)
    \tkzMarkRightAngle[color=red,size=.15](I,tkzPointResult,B)
    \tkzDrawAltitude(C,A)(I)
    \tkzMarkRightAngle[color=red,size=.15](I,tkzPointResult,C)
    \end{tikzpicture}An
    \caption{Inscribed circle.}    
    \end{figure}  

\end{document}

Answer 2

I think that drawing the bisectors increases the bounding box. You can avoid this by interrupting the box while drawing them.

\documentclass{article}
\usepackage{amsmath}
\usepackage{tikz}
\usepackage{tkz-euclide}
\usetkzobj{all}

\begin{document}
\begin{figure}
  \centering
  \begin{tikzpicture}
    \tkzDefPoint(0,0){A}
    \tkzDefPoint(5,0){B}
    \tkzLabelPoints[below](A)
    \tkzLabelPoints[below](B)
    \tkzDrawSegment(A,B)
    \tkzDefPoint(2,3){C}
    \tkzLabelPoints[above](C)
    \tkzDrawSegment(A,C)
    \tkzDrawSegment(B,C)
    \begin{pgfinterruptboundingbox}
    \tkzDrawBisector(C,B,A)(P)
    \tkzDrawBisector(C,A,B)(Q)
    \tkzDrawBisector(A,C,B)(R)
    \end{pgfinterruptboundingbox}
    \tkzDefCircle[in](A,B,C)\tkzGetPoint{I}\tkzGetLength{rIN}
    \tkzDrawCircle[R](I,\rIN pt)
    \draw[red] (I) -- ($(A)!(I)!(C)$)++(-30:0.1) -- ++(56:0.1) -- +(-34:-0.1);
    \draw[red] (I) -- ($(A)!(I)!(B)$) ++(90:0.1) -- ++(0:-0.1) -- +(-90:0.1);
    \draw[red] (I) -- ($(B)!(I)!(C)$) ++(45:-0.1) -- ++(-45:0.1) -- +(45:0.1);
    \draw (I)+(.2,-.3) node {$I$};
  \end{tikzpicture}
  \caption{Inscribed circle.}
\end{figure}
\end{document}

Here's a comparison of the figure with the unmodified code (Before) and the modified code (After):

Answer 3

Another potential solution, the sledgehammer method, so to say, would be to insert an \vspace*{-3.2cm} between the \end{tikzpicture} and \caption{Inscribed circle.}. With this, you can remove the space, but it does only address the symptom of the problem but not the cause.