# functions of variables with matrices

I am trying to make a function of a variable with sage for example:

```
f(x) = sin(x)
f(x+y)
```

yields:

```
sin(x+y)
```

However if It is in a matrix this no longer works:

```
f(x) = matrix([[sin(x)],[cos(x)]])
f(x+y)
```

yields:

```
sin(x)
cos(x)
```

Is this not possible or am I missing something to make this work?

I am using sage 7.3 on Ubuntu 16.04 with the aims ppa.