# MATLAB: Tangents to the curves

graphstangents

Hello, I have plotted a few figures as shown below. Now i would like to plot the tangents to each of these curves. How can i do that?
I have searched on the forum but could not get any definitive answer.
The code for this graph is divided in 2 functions as shown below:
function [x,y_val] = plot_trial(Z)g = 9.8; K = 0.3; % g is the gravitational acclerationy = @(V_d) (1/(2*g*K^2))*(V_d.^2/Z^2);x = linspace(0,1,100);y_val = y(x);endclc; clear; close all;% Use the other function 'plot_trial()'[v_d1, y_val1] = plot_trial(1);[~,y_val2]= plot_trial(2);[~,y_val3]= plot_trial(3);figurehold onplot(v_d1, y_val1,v_d1,y_val2,v_d1,y_val3)legend('Z=1','Z=2','Z=3')title('Der Tank (Konstante Querschnittsfläche)')xlabel('dV1/dt')ylabel('Y') x = linspace(0, 5);y = x.^2;h = x(2)-x(1);dydx = gradient(y, h);xi = 2.1;                                       % Choose An ‘x’ Valueyi = interp1(x, y, xi);                         % Corresponding ‘y’ Valuedydxi = interp1(x, dydx, xi);                   % Derivative At ‘x’intcpt = yi - dydxi*xi;                         % Calculate Y-Interceptfigureplot(x, y, '-b')hold onplot(x, dydxi*x+intcpt, '-r')hold offgridlegend('Data','Tangent', 'Location','NW') 