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] (I) circle[radius=sqrt(5)];
\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,red] (I) circle[radius=2cm];
\draw[thick,blue] (d1) node[above]{$d$}--(M)--(H)--(N)--(A)--(d2);
\draw (M)--(I)--(H);
\draw pic [draw,black,angle radius=3mm] {right angle=M--H--I};
\draw[|| mark=0.5] (H)--(M);
\draw[|| mark=0.5] (H)--(N);
\foreach \x/\g in {M/110,N/70,H/90,A/-90,I/-90}
\draw[fill=white] (\x) circle (1.5pt)+(\g:3mm) node {$\x$};
\end{tikzpicture}