DrRacket/Scheme circle undefined
<p>I'm a beginner learning Scheme. I tried to follow the <a href="https://docs.racket-lang.org/quick/" rel="nofollow">quick introduction</a> to get familiar with the syntax, but stuck in step 3. When I type (circle 10), it gives me "circle: undefined;
 cannot reference an identifier before its definition" Do I miss some library or I have to define circle first?</p>

<p><a href="http://i.stack.imgur.com/HVPtR.png" rel="nofollow">output error</a></p>