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

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

@@ -98,6 +98,11 @@ public class NaiveNumber implements NumberInterface {
         return (int) Math.ceil(value);
     }
 
+    @Override
+    public int floor() {
+        return (int) Math.floor(value);
+    }
+
     @Override
     public NumberInterface promoteTo(Class<? extends NumberInterface> toClass) {
         if (toClass == this.getClass()) return this;

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

@@ -85,6 +85,12 @@ public interface NumberInterface {
      */
     int ceiling();
 
+    /**
+     * Return the greatest integer less than or equal to the number.
+     * @return the greatest int >= the number, if int can hold the value.
+     */
+    int floor();
+
     /**
      * Promotes this class to another number class.
      *

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());