degre2.py

Created on January 22, 2021

755 Bytes

Trace une courbe du second degré, à partir de coefficients a,b, et c que vous donnez.

from math import sqrt 
from matplotlib import pyplot as plt
from mathsup import disc

a = float(input("a = "))
b = float(input("b = "))
c = float(input("c = "))

x = -10, 10, 0.1

def f(x,a,b,c):
    return a*x**2+b*x+c

y = f(x,a,b,c)

plt.plot(x,y,"red")

plt.grid(True)

if a != 0 and disc(a,b,c) >= 0:
    delta = disc(a,b,c)
    if delta == 0:
        x0 = -b/2*a
        plt.text(x0, f(x0,a,b,c), "x0")
    else:
        x1 = (-b+sqrt(delta))/(2*a)
        x2 = (-b-sqrt(delta))/(2*a)
        plt.text(x1, f(x1,a,b,c), "x1 = " + str(x1))
        plt.text(x2, f(x2,a,b,c), "x2 = " + str(x2))


plt.title("Courbe Cf (en rouge) de la fonction f = " + str(a) + "x2+" + str(b) + "x+" + str(c))
plt.ylabel("f(x)")
plt.xlabel("x")

plt.show()