### Multiplying elements of D4

I have the following group presentation $D_4 = \langle r,s | r^4 = s^2 = rsrs = 1 \rangle$.

This is written in sage as

```
F.<r,s> = FreeGroup()
D4 = F / [r^4, s^2, r*s*r*s, 1]
r,s = D4.gens()
```

Say I wanted to compute s^2, this should equal 1 but sage gives me just s^2.

```
s^2
```

output:

```
s^2
```

I am doing more involved calculations and I want to return the result in the simplified form. How do I simplify the expression in sage?