math module makes confusing!

Question

>>> import math
>>> math.cos(math.pi/2)
6.123233995736766e-17
>>> math.acos(0)
1.5707963267948966
>>> math.pi/2
1.5707963267948966

As I learn cos(pi/2) = 0 that means acos(0) = pi/2
why cos(pi/2) = 6.123233995736766e-17

Answer 1

You could read up more in the python stuff on their documentationsfof each version.
Search Python Documentation on Google

Answer 2

This actually *is* zero, with a floating-point accuracy! ;)
https://en.m.wikipedia.org/wiki/Floating-point_arithmetic#Accuracy_problems

Answer 3

in advance,the PI representation is not real but it is also truncated with an appropriate accuracy and its half has less accuracy than in real.This is caused by mashine representation of decimal number(floating points operations).

Answer 4

Ahha! I got it @sayan chandra.

Answer 5

here is it...check the output against each line of code...

https://code.sololearn.com/cI1NCJ9BwpBA/?ref=app

Answer 6

see this second verson of explaination

@SENG THAI
Red all the comments in code.

https://code.sololearn.com/cCo62gBgC4kG/?ref=app

Answer 7

@sayan chandra Thanks! But Why it shows up as exponential value. It is because it can not show all the floating number after ".", isn't it?

Answer 8

of course..
exactly

Answer 9

somewhere anyway u have to end...
cause this floating points hav no end..
like 10 divided by 3....