santiagobasulto - 1 year ago 71

Python Question

I'm having a little problem, take a look:

`>>> import math`

>>> math.sin(math.pi)

1.2246467991473532e-16

This is not what I learnt in my Calculus class (It was 0, actually)

So, now, my question:

I need to perform some heavy trigonometric calculus with Python. What library can I use to get correct values?

Can I use Decimal?

EDIT:

Sorry, What I mean is other thing.

What I want is some way to do:

`>>> awesome_lib.sin(180)`

0

or this:

`>>> awesome_lib.sin(Decimal("180"))`

0

I need a libraray that performs good trigonometric calculus. Everybody knows that sin 180° is 0, I need a library that can do that too.

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Answer Source

`1.2246467991473532e-16`

is close to 0 -- there are 16 zeroes between the decimal point and the first significant digit -- much as `3.1415926535897931`

(the value of `math.pi`

) is close to pi. The answer is correct to sixteen decimal places!

So if you want `sin(pi)`

to equal 0, simply round it to a reasonable number of decimal places. 15 looks good to me and should be plenty for any application:

```
print round(math.sin(math.pi), 15)
```