Find a function `FUN`

that leads to the following output:

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

##
**Answer 1: click to reveal**

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))
curve(sin, add = TRUE)
grid()
```

##
**Answer 2: click to reveal**

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))
curve(sin, add = TRUE)
grid()
```

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