pom.xml

                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
                 <configuration>
-                    <source>1.7</source>
-                    <target>1.7</target>
+                    <source>8</source>
+                    <target>8</target>
                 </configuration>
             </plugin>
         </plugins>

src/main/java/rocks/zipcode/calcskin/CalcEngine.java

     }
 
     public double add(double v, double v1) {
-        return Double.NaN;
+        return v+v1;
     }
 
     public double subtract(double v, double v1) {
-        return Double.NaN;
+        return v-v1;
     }
 
     public double multiply(double v, double v1) {
-        return Double.NaN;
+        return v*v1;
     }
 
     public double divide(double v, double v1) {
-        return Double.NaN;
+        return v/v1;
     }
+    public double square(double v)
+    {
+        return Math.pow(v, 2.0);
+    }
+
+    public double root(double v) {
+        return Math.sqrt(v);
+    }
+
+    public double inverse(double v){
+        return 1.0 / v;
+    }
+
+    public double expo(double v, double v1) {
+        return Math.pow(v, v1);
+    }
+
+    public double tan(double v) {
+        return Math.tan(v);
+    }
+
+    public double log(double v) {
+        return Math.log10(v);
+    }
+
+    public double sin(double v) {
+        return Math.sin(v);
+    }
+
+    public double cos(double v) {
+        return Math.cos(v);
+    }
+
+    public double atan(double v) {
+        return Math.atan(v);
+    }
+
+    public double asin(double v) {
+        return Math.asin(v);
+    }
+
+    public double acos(double v) {
+        return Math.acos(v);
+    }
+
 }

src/main/java/rocks/zipcode/calcskin/CalcSkin.java

 
 import javafx.application.Application;
 import javafx.beans.binding.Bindings;
-import javafx.beans.property.*;
+import javafx.beans.property.DoubleProperty;
+import javafx.beans.property.ObjectProperty;
+import javafx.beans.property.SimpleDoubleProperty;
+import javafx.beans.property.SimpleObjectProperty;
 import javafx.event.ActionEvent;
 import javafx.event.EventHandler;
 import javafx.geometry.Pos;
 import javafx.scene.Scene;
-import javafx.scene.control.*;
+import javafx.scene.control.Button;
+import javafx.scene.control.TextField;
 import javafx.scene.input.KeyEvent;
-import javafx.scene.layout.*;
+import javafx.scene.layout.TilePane;
+import javafx.scene.layout.VBox;
 import javafx.stage.Stage;
 import javafx.stage.StageStyle;
-import rocks.zipcode.calcskin.CalcEngine;
 
 import java.util.HashMap;
 import java.util.Map;
         });
     }
 }
-
-