I have this function that takes in an x value and returns an output y value.
def function(x):
y = math.cos(x**2/2)/(math.log(x+2,2))
return y
When I call the function, I get:
print function(1)
>> 0.630929753571
But WolframAlpha has the value at x = 1 to be 0.553693
Which is the correct value?
This is because you are using Python 2, where the / operator does integer division. This would give you the correct answer in Python 3:
>>> def f(x):
... y = math.cos(x**2/2)/(math.log(x+2,2))
... return y
...
>>> f(1)
0.5536929495121011
In Python 3, using the // operator, does floor division:
>>> def f(x):
... y = math.cos(x**2//2)/(math.log(x+2,2))
... return y
...
>>> f(1)
0.6309297535714574
>>>
In Python 2, use y = math.cos(x**2/ 2.0) / (math.log(x+2,2))
you are dividing an int by another int which is greater: 1 / 2 and therefore getting the cosine of zero since python 2.7 does not evaluate integer divisions as floating point. Try:
def function(x):
y = math.cos(x ** 2 / 2.0) / (math.log(x + 2, 2))
return y
Python 2 division operator does integer division, unless you tell it it's a float.
If you change to x**2/2.0 you will get the correct answer, like wolfram alfa.
Python 2 rounds to integer when you divide integer by integer so use one float number (i.e 2.0) when you divide to get correct result
import math
def function(x):
y = math.cos(x**2/2.0)/(math.log(x+2,2))
return y
print function(1)
