# Một số hình vẽ tặng thầy Trần Quản Lộ Dù gì cũng bỏ công vẽ vời, thôi thì lưu lại sản phẩm code this, code that để làm kỹ niệm. \begin{tikzpicture}[>=stealth,line join=round, line cap=round, scale=1]
\coordinate (B) at (0,0);
\coordinate (A) at (1.5,3);
\coordinate (C) at (4,0);
\coordinate (K) at ($(B)!(A)!(C)$);
\coordinate (I) at ($(A)!(B)!(C)$);
\path[name path=l1] (A)--(K);
\path[name path=l2] (B)--(I);
\path[name intersections={of=l1 and l2, by=H}];
\draw[thick] (I)--(B)--(C)--(A)--(B) (A)--(K);
\kihieuvuong[size=6pt](C,K,A);
\kihieuvuong[size=6pt](B,I,C);
\foreach \x/\g in {A/90,B/-90,C/-90,I/45,K/-90,H/135}
\draw[fill=white] (\x) circle (1.5pt)+(\g:3mm) node {$\x$};
\end{tikzpicture} \begin{tikzpicture}[>=stealth,line join=round, line cap=round, scale=1,
|| mark/.style={postaction=decorate,decoration={markings,
mark=at position #1 with {\draw[line cap=round,mark segment] (-1pt,-2pt) -- (-1pt,2pt);
\draw[line cap=round,mark segment] (1pt,-2pt) -- (1pt,2pt);
}}},mark segment/.style={thick},
| mark/.style={postaction=decorate,decoration={markings,
mark=at position #1 with {\draw[line cap=round,mark segment] (-1pt,-2pt) -- (-1pt,2pt);}}},mark segment/.style={thick}]
\coordinate (I) at (0,1);
\coordinate (B) at (-2,0);
\coordinate (C) at (2,0);
\coordinate (A) at ($(I)!1!150:(C)$);
\coordinate (M) at ($(A)!0.5!(B)$);
\coordinate (N) at ($(B)!0.5!(C)$);
\coordinate (A1) at ($(I)!2!(M)$);
\coordinate (A2) at ($(M)!2.5!(I)$);
\coordinate (B1) at ($(I)!2!(N)$);
\coordinate (B2) at ($(N)!2.5!(I)$);
\draw[thick] (A)--(B)--(C)--(A);
\draw (A1) node[above]{$d_1$}--(A2) (B1)--(B2) node[right]{$d_2$};
\draw[| mark=0.5] (M)--(A);
\draw[| mark=0.5] (M)--(B);
\draw[|| mark=0.5] (N)--(B);
\draw[|| mark=0.5] (N)--(C);
\kihieuvuong[size=6pt](B,M,I);
\kihieuvuong[size=6pt](C,N,I);
\foreach \x/\g in {A/110,B/200,M/110,N/-135,C/-30,I/30}
\draw[fill=white] (\x) circle (1.5pt)+(\g:3mm) node {$\x$};
\end{tikzpicture} \begin{tikzpicture}[>=stealth,line join=round, line cap=round, scale=1,
|| mark/.style={postaction=decorate,decoration={markings,
mark=at position #1 with {\draw[line cap=round,mark segment] (-1pt,-2pt) -- (-1pt,2pt);
\draw[line cap=round,mark segment] (1pt,-2pt) -- (1pt,2pt);
}}},mark segment/.style={thick}]
\coordinate (B) at (0,0);
\coordinate (A) at (2,3);
\coordinate (C) at (5,0);
\coordinate (M) at ($(B)!0.5!(C)$);
\draw[thick] (M)--(A)--(B)--(C)--(A);
\draw[|| mark=0.5] (M)--(B);
\draw[|| mark=0.5] (M)--(C);
\foreach \x/\g in {A/90,B/-90,M/-90,C/-90}
\draw[fill=white] (\x) circle (1.5pt)+(\g:3mm) node {$\x$};
\end{tikzpicture} \begin{tikzpicture}[>=stealth,line join=round, line cap=round, scale=1]
\coordinate (d11) at (-1,0);
\coordinate (d12) at (6,0);
\coordinate (d21) at (-0.5,-0.5);
\coordinate (d22) at (4,4);
\coordinate (A) at (0,0);
\coordinate (B) at (4,0);
\coordinate (C) at (4,2);
\coordinate (D) at ($(d21)!(C)!(d22)$);
\coordinate (C1) at ($(D)!1.5!(C)$);
\coordinate (C2) at ($(B)!1.5!(C)$);
\draw pic["$\varphi$",draw=blue,double,-,angle eccentricity=1.5, angle radius=0.5cm] {angle=B--A--D};
\draw pic["$2$",draw=blue,double,-,angle eccentricity=1.4, angle radius=0.5cm] {angle=B--C--C1};
\draw pic["",draw=blue,double,-,angle eccentricity=1.4, angle radius=0.5cm] {angle=C2--C--D};
\draw pic["$1$",draw=magenta,-,angle eccentricity=1.4, angle radius=0.5cm] {angle=C1--C--C2};
\draw[thick,red] (d11)--(d12) node[below]{$\Delta_1$} (d21)--(d22) node[right]{$\Delta_2$};
\draw[thick,dashed] (D)--(C)--(B);
\draw[thick,blue,->] (C)--(C1) node[right]{$\overrightarrow{n_2}$};
\draw[thick,blue,->] (C)--(C2) node[right]{$\overrightarrow{n_1}$};
\kihieuvuong[size=8pt](d12,B,C);
\kihieuvuong[size=8pt](C,D,d22);
\foreach \x/\g in {A/90,B/-90,C/200,D/120}
\draw[fill=white] (\x) circle (1.5pt)+(\g:3mm) node {$\x$};
\end{tikzpicture} \begin{tikzpicture}[>=stealth,line join=round, line cap=round, scale=1]
\coordinate (d11) at (-2,0);
\coordinate (d12) at (4.5,0);
\coordinate (d21) at (-2,-1);
\coordinate (d22) at (4,2);
\coordinate (A) at (0,0);
\draw pic["$2$",draw=blue,double,-,angle eccentricity=1.3, angle radius=0.8cm] {angle=d12--A--d22};
\draw pic["$4$",draw=blue,double,-,angle eccentricity=1.3, angle radius=0.8cm] {angle=d11--A--d21};
\draw pic["$1$",draw=red,-,angle eccentricity=1.4, angle radius=0.5cm] {angle=d21--A--d12};
\draw pic["$3$",draw=red,-,angle eccentricity=1.4, angle radius=0.5cm] {angle=d22--A--d11};
\draw[thick] (d11)--(A) node[below]{$A$}--(d12) node[below]{$\Delta_1$} (d21)--(d22) node[right]{$\Delta_2$};
\end{tikzpicture} \begin{tikzpicture}[>=stealth,line join=round, line cap=round, scale=1]
\coordinate (d11) at (-1,0);
\coordinate (d12) at (5,0);
\coordinate (d21) at (-0.5,-0.5);
\coordinate (d22) at (4,4);
\coordinate (E) at (0,0);
\coordinate (F) at (2,0);
\coordinate (G) at (2,2);
\coordinate (K) at (2,4);
\coordinate (H) at ($(G)!(K)!(d22)$);
\coordinate (n1) at ($(K)!-0.7!(G)$);
\coordinate (n2) at ($(K)!-1!(H)$);
\draw pic["$\varphi$",draw=blue,double,-,angle eccentricity=1.5, angle radius=0.5cm] {angle=F--E--G};
\draw pic["$1$",draw=blue,-,angle eccentricity=1.4, angle radius=0.5cm] {angle=G--K--H};
\draw pic["$2$",draw=blue,double,-,angle eccentricity=1.4, angle radius=0.5cm] {angle=n1--K--n2};
\draw[thick,red] (d11)--(d12) node[below]{$\Delta_1$} (d21)--(d22) node[right]{$\Delta_2$};
\draw[thick,dashed] (F)--(K)--(H);
\draw[thick,blue,->] (K)--(n1) node[right]{$\overrightarrow{n_1}$};
\draw[thick,blue,->] (K)--(n2) node[left]{$\overrightarrow{n_2}$};
\kihieuvuong[size=8pt](d12,F,G);
\kihieuvuong[size=8pt](d22,H,K);
\foreach \x/\g in {E/90,F/-90,G/-45,H/-45,K/0}
\draw[fill=white] (\x) circle (1.5pt)+(\g:3mm) node {$\x$};
\end{tikzpicture} \begin{tikzpicture}[>=stealth,line join=round, line cap=round, scale=1]
\coordinate (d11) at (-1,0);
\coordinate (d12) at (5,0);
\coordinate (d21) at (-0.5,-0.5);
\coordinate (d22) at (4,4);
\coordinate (E) at (0,0);
\coordinate (F) at (2,0);
\coordinate (G) at (2,2);
\coordinate (K) at (2,4);
\coordinate (H) at ($(G)!(K)!(d22)$);
\coordinate (n1) at ($(K)!-0.7!(G)$);
\coordinate (n2) at ($(K)!-1!(H)$);
\coordinate (I) at ($(E)!0.5!(K)$);
\draw pic["$\varphi$",draw=blue,double,-,angle eccentricity=1.5, angle radius=0.5cm] {angle=F--E--G};
\draw pic["$1$",draw=blue,-,angle eccentricity=1.4, angle radius=0.5cm] {angle=G--K--H};
\draw pic["$2$",draw=blue,double,-,angle eccentricity=1.4, angle radius=0.5cm] {angle=n1--K--n2};
\draw[thick,red] (d11)--(d12) node[below]{$\Delta_1$} (d21)--(d22) node[right]{$\Delta_2$};
\draw[thick,dashed] (F)--(K)--(H);
\draw[thick,blue,->] (K)--(n1) node[right]{$\overrightarrow{n_1}$};
\draw[thick,blue,->] (K)--(n2) node[left]{$\overrightarrow{n_2}$};
\kihieuvuong[size=8pt](d12,F,G);
\kihieuvuong[size=8pt](d22,H,K);
\draw[thick,red] let \p1=($(K)-(I)$) in (I) circle ({veclen(\x1,\y1)});
\foreach \x/\g in {E/90,F/-90,G/-45,H/-45,K/0}
\draw[fill=white] (\x) circle (1.5pt)+(\g:3mm) node {$\x$};
\end{tikzpicture} \begin{tikzpicture}[line join=round, line cap=round,|| mark/.style={postaction=decorate,decoration={markings,
mark=at position #1 with {\draw[line cap=round,mark segment] (-1pt,-2pt) -- (-1pt,2pt);
\draw[line cap=round,mark segment] (1pt,-2pt) -- (1pt,2pt);
}}},mark segment/.style={thick}]
\coordinate (I) at (0,0);
\coordinate (N) at (30:2cm);
\coordinate (M) at (150:2cm);
\coordinate (H) at ($(M)!0.5!(N)$);
\coordinate (d1) at ($(N)!1.5!(M)$);
\coordinate (d2) at ($(M)!1.5!(N)$);
\coordinate (A) at ($(M)!1.4!(N)$);
\draw[thick,blue] (d1) node[above]{$d$}--(M)--(H)--(N)--(A)--(d2);
\draw[fill=white] (\x) circle (1.5pt)+(\g:3mm) node {$\x$};
\end{tikzpicture}