from math import*
def dichotomie(n):
   a = 0.5
   b = pi/2+0.5
   while abs(b-a) > 1/(10^n):
      c =(a+b)/2
      if 3*cos(2*c-1) > 0 :
         a = c
      else :
         b = c
   print("Une valeur approchée de x est comprise entre",a,"et",b)