# Basic trigonometric simplifications in Symbolics.jl

**URL:** <https://discourse.julialang.org/t/basic-trigonometric-simplifications-in-symbolics-jl/99507>\
**Category:** General Usage\
**Tags:** question\
**Created:** [May 28, 2023, 8:36am UTC](https://discourse.julialang.org/t/basic-trigonometric-simplifications-in-symbolics-jl/99507 "2023-05-28T08:36:01Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![pr0physicist](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/pr0physicist/32/36270_2.png) [@pr0physicist](https://discourse.julialang.org/u/pr0physicist)\
**Post date:** [May 28, 2023, 8:36am UTC](https://discourse.julialang.org/t/basic-trigonometric-simplifications-in-symbolics-jl/99507/1 "2023-05-28T08:36:01Z")

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Julia: v1.9.0  
Symbolics.jl: v5.3.1

Not sure if this is the intended behavior:

```julia
using Symbolics

@variables x

simplify(sin(x) + sin(-x))

```

returns

```julia
sin(x) + sin(-x)

```

instead of 0, which is really surprising. Then checked if I could write down a rewriting rule using SymbolicUtils.jl like this:

```julia
using SymbolicUtils

@syms a
r = @rule sin(-(~a)) => -sin(~a)
r(sin(-a))

```

which prints nothing! Am I doing something wrong here?

---

<div class="post-metadata">

**Author:** ![drandran12](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/drandran12/32/220647_2.png) [@drandran12](https://discourse.julialang.org/u/drandran12)\
**Post date:** [August 2, 2024, 6:07pm UTC](https://discourse.julialang.org/t/basic-trigonometric-simplifications-in-symbolics-jl/99507/2 "2024-08-02T18:07:35Z")

</div>

Having the same problem here. Anyone that can help?