
Tengo algunos problemas de escala al dibujar diagramas con TIKZ. Tengo un casco convexo. Deseo dibujar una parábola que pase por los dos primeros vértices distintos de cero del casco convexo (a y b respectivamente). Calculé los coeficientes para que la parábola pase por los dos primeros vértices distintos de cero del casco convexo. Aunque uniformé la escala, no puedo obtener el resultado deseado. Aquí está MWE
\documentclass[crop,tikz]{standalone}
\begin{document}
\begin{tikzpicture}[scale=.35]
\draw[draw=none,scale=5](0,0)--(-1.1730,0.9848)--(-1.5,0.8660)--(-1.7660,0.6428)--(-1.9397,0.3420)--(-1.9397,-0.3420)--(-1.7660,-0.6428)--(-1.5,-0.8660)--(-1.1730,-0.9848)--(0,0)--cycle;
\draw[thick,scale=5,color=black] (0,0)--(-1.1730,0.9848)--(-1.5,0.8660)--(-1.7660,0.6428)--(-1.9397,0.3420);
\draw[thick,scale=5] (-1.9397,-0.3420)--(-1.7660,-0.6428)--(-1.5,-0.8660)--(-1.1730,-0.9848)--(0,0);
\draw[scale=5, domain=-2:2, smooth, variable=\y, red] plot ({1.48720*\y*\y+2.615340}, {\y});
\node[] at (0.75,0.75) {$0$};
\node[] at (-5.75,5.5) {$a$};
\node[] at (-7.5,5.0) {$b$};
\draw[thick,->,,>=stealth] (-11.5,0)--(2,0) node[right]{$X$};
\draw[thick,->,,>=stealth] (0,-8)--(0,8) node[above]{$Y$};
\end{tikzpicture}
\end{document}
Respuesta1
Intento reproducir tus imágenes:
\documentclass[margin=3mm, tikz]{standalone}
\begin{document}
\begin{tikzpicture}[
T/.style = {font=\scriptsize, fill=white, inner sep=1pt},% ticks
dot/.style = {circle, fill, inner sep=1pt},
scale = 2]
% axis
\draw[thick,-stealth] (-3,0) -- (2,0) node[right] {$X$};
\draw[thick,-stealth] (0,-2) -- (0,2) node[above]{$Y$};
\foreach \i in {-2.5,-2,...,1.5}
\draw (\i,1mm) -- ++ (0,-2mm) node[T, below] {\i};
\foreach \i in {-1.5,-1,-0.5,0.5,1,1.5}
\draw (1mm,\i) -- ++ (-2mm,0) node[T, left] {\i};
% rotated parabola
\draw[domain=0:1.2, variable=\y,
red, very thick] (-3,0) -- plot (3*\y*\y-2.5, \y);%- 1.00456
% a and b points on parabola
\node (a) [dot,label=$a$] at (3*0.5*0.5-2.5,0.5) {};
\node (b) [dot,label=$b$] at (3*0.6*0.6-2.5,0.6) {};
% line
\draw (a) -- ++ (-0.4,-0.3) node[dot] {}
-- ++ (0,-1.2) node[dot] {}
-- ++ (0.4,-0.2) node[dot] {}
-- ++ (0.5,-0.1) node[dot] {}
-- (0,0) node[dot] {}
-- (b);
\end{tikzpicture}
\end{document}