Result error in implementation of trigonometric function by Newton Raphson method in PYTHON

Question

trigonometric function by Newton method is giving wrong results

def func(x):
    return radians(math.sin(x)+log(x)+1)

def derivFunc(x):
    return radians((1/x) + math.cos(x))

#sin(x)+log(x)+1 --is the function i want to apply method on

**# Function to find the root**
def newtonRaphson(x):
    h = func(x) / derivFunc(x)
    while abs(h) >= 0.0001:
        h = func(x) / derivFunc(x)
        # x(i+1) = x(i) - f(x) / f'(x)
        x = x - h
    print("The value of the root is : ",
          "%.4f" % x)

x0 = 0.03  
newtonRaphson(x0)

I see `deriveFunc`, where is `func`? – Alan Hoover Jun 19 '20 at 17:24 — Alan Hoover, Jun 19 '20 at 17:24
@AlanHoover its there now .. some editing mistake – ashiq pervez Jun 19 '20 at 17:52 — ashiq pervez, Jun 19 '20 at 17:52

score 0 · Accepted Answer · edited Jun 19 '20 at 20:35

0

The problem is the radians, which multiplies a part of an expression by pi/180.0. Remove all of its mentions, and it should be fine.

EDIT

The below works absolutely fine now:

import math
def func(x):
    return math.sin(x)+math.log10(x)+1

def derivFunc(x):
    return (1/x) + math.cos(x)
#sin(x)+log(x)+1 --is the function i want to apply method on

# Function to find the root
def newtonRaphson(x):
    h = func(x) / derivFunc(x)
    while abs(h) >= 0.0001:
        h = func(x) / derivFunc(x)
        # x(i+1) = x(i) - f(x) / f'(x)
        x = x - h
    print("The value of the root is : ",
          "%.4f" % x)

 x0 = 0.03  
 newtonRaphson(x0)

edited Jun 19 '20 at 20:35

ashiq pervez

45
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answered Jun 19 '20 at 18:10

Igor Rivin

4,632
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35

and what about the sin and cos... as in calculator we have to set mode to RADIAN in order to obtain correct results ... here it is not working properly with or without radian giving the same answer – ashiq pervez Jun 19 '20 at 18:18
@ashiqpervez This is not a calculator. The code in the answer (basically yours, with typos fixed and radians removed) works fine. – Igor Rivin Jun 19 '20 at 18:32
still same previous results – ashiq pervez Jun 19 '20 at 18:44
1

@ashiqpervez I get: The value of the root is : 0.2793 which is correct. – Igor Rivin Jun 19 '20 at 18:52
i am getting the same .. but correct value is 0.082 – ashiq pervez Jun 19 '20 at 18:55
@ashiqpervez Plug in the value into sin(x) + log(x) +1, and see that you get close to zero. – Igor Rivin Jun 19 '20 at 19:02

Result error in implementation of trigonometric function by Newton Raphson method in PYTHON

1 Answers1