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Find a function `FUN` that leads to the following output:

```curve(FUN, from = -10, to = 10, col = "red", ylim = c(-2, 2))
grid()```

Hint: aim to keep the answer simple. The main logic of the function can often be summarized in a single line of R code.

We can write the function as follows:

```  FUN <- function(x) {
return(sin(x + pi / 2))
}```

We then get:

```  curve(FUN, from = -10, to = 10, col = "red", ylim = c(-2, 2))
grid()```

We can use various trigonometric identities to derive more solutions to this puzzle. For example:

sin(x + pi/2) = cos(x)

`FUN` can then be defined as:

```  FUN <- function(x) {
return(cos(x))
}```

We can confirm that this function solves the puzzle:

```  curve(FUN, from = -10, to = 10, col = "red", ylim = c(-2, 2))