# Cos(pi/2) does not return 0

**URL:** <https://discourse.julialang.org/t/cos-pi-2-does-not-return-0/27081>\
**Category:** General Usage\
**Created:** [August 1, 2019, 4:22pm UTC](https://discourse.julialang.org/t/cos-pi-2-does-not-return-0/27081 "2019-08-01T16:22:40Z")\
**Posts on this page:** 1\
**Showing post:** 2

<div class="post-metadata">

**Author:** ![Tamas\_Papp](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tamas_papp/32/25949_2.png) [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)\
**Post date:** [August 1, 2019, 4:35pm UTC](https://discourse.julialang.org/t/cos-pi-2-does-not-return-0/27081/2 "2019-08-01T16:35:25Z")

</div>

Not intended, but hard to avoid because of floating point error. See

> [@PSA: floating-point arithmetic](https://discourse.julialang.org/t/psa-floating-point-arithmetic/8678):
>
> Sometimes people are surprised by the results of floating-point calculations such as julia\> 5/6 0.8333333333333334 # shouldn't the last digit be 3? julia\> 2.6 - 0.7 - 1.9 2.220446049250313e-16 # shouldn't the answer be 0? These are not bugs in Julia. They’re consequences of the IEEE-standard 64-bit binary representation of floating-point numbers that is burned into computer hardware, which Julia and many other languages use by default. Brief explanation You can t…

You can use

```julia
julia> cospi(0.5)
0.0

```

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_[View the full topic](https://discourse.julialang.org/t/cos-pi-2-does-not-return-0/27081)._