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There are three methods that find approximately the roots of a non-linear function
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MindTraper 2017-12-17 22:02:36 +02:00 committed by GitHub
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Bisection.py Normal file
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import math
def bisection(function, a, b): # finds where the function becomes 0 in [a,b] using bolzano
start = a
end = b
if function(a) == 0: # one of the a or b is a root for the function
return a
elif function(b) == 0:
return b
elif function(a) * function(b) > 0: # if noone of these are root and they are both possitive or negative,
# then his algorith can't find the root
print("couldn't find root in [a,b]")
return
else:
mid = (start + end) / 2
while abs(start - mid) > 0.0000001: # untill we achive percise equals to 10^-7
if function(mid) == 0:
return mid
elif function(mid) * function(start) < 0:
end = mid
else:
start = mid
mid = (start + end) / 2
return mid
def f(x):
return math.pow(x, 3) - 2*x -5
print(bisection(f, 1, 1000))

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Intersection.py Normal file
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import math
def intersection(function,x0,x1): #function is the f we want to find its root and x0 and x1 are two random starting points
x_n = x0
x_n1 = x1
while True:
x_n2 = x_n1-(function(x_n1)/((function(x_n1)-function(x_n))/(x_n1-x_n)))
if abs(x_n2 - x_n1)<0.00001 :
return x_n2
x_n=x_n1
x_n1=x_n2
def f(x):
return math.pow(x,3)-2*x-5
print(intersection(f,3,3.5))

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NeutonMethod.py Normal file
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import math
def newton(function,function1,startingInt): #function is the f(x) and function1 is the f'(x)
x_n=startingInt
while True:
x_n1=x_n-function(x_n)/function1(x_n)
if abs(x_n-x_n1)<0.00001:
return x_n1
x_n=x_n1
def f(x):
return math.pow(x,3)-2*x-5
def f1(x):
return 3*math.pow(x,2)-2
print(newton(f,f1,3))