Implement sin function and helper functions such as getSmallAngle and floor.

src/main/java/org/nwapw/abacus/number/PreciseNumber.java

@@ -100,6 +100,11 @@ public class PreciseNumber implements NumberInterface {
         return (int) Math.ceil(value.doubleValue());
     }
 
+    @Override
+    public int floor() {
+        return (int) Math.floor(value.doubleValue());
+    }
+
     @Override
     public NumberInterface negate() {
         return new PreciseNumber(value.negate());