diff --git a/src/com/bytezone/diskbrowser/visicalc/Acos.java b/src/com/bytezone/diskbrowser/visicalc/Acos.java
new file mode 100644
index 0000000..c7ef27a
--- /dev/null
+++ b/src/com/bytezone/diskbrowser/visicalc/Acos.java
@@ -0,0 +1,30 @@
+package com.bytezone.diskbrowser.visicalc;
+
+public class Acos extends Function
+{
+  Value v;
+
+  Acos (Sheet parent, Cell cell, String text)
+  {
+    super (parent, cell, text);
+
+    v = new Expression (parent, cell, functionText).reduce ();
+    valueType = ValueType.VALUE;
+  }
+
+  @Override
+  public void calculate ()
+  {
+    v.calculate ();
+    if (!v.isValueType (ValueType.VALUE))
+    {
+      valueType = v.getValueType ();
+      return;
+    }
+
+    value = Math.acos (v.getValue ());
+
+    if (Double.isNaN (value))
+      valueType = ValueType.ERROR;
+  }
+}
\ No newline at end of file
diff --git a/src/com/bytezone/diskbrowser/visicalc/Asin.java b/src/com/bytezone/diskbrowser/visicalc/Asin.java
new file mode 100644
index 0000000..cb4b1e5
--- /dev/null
+++ b/src/com/bytezone/diskbrowser/visicalc/Asin.java
@@ -0,0 +1,30 @@
+package com.bytezone.diskbrowser.visicalc;
+
+public class Asin extends Function
+{
+  Value v;
+
+  Asin (Sheet parent, Cell cell, String text)
+  {
+    super (parent, cell, text);
+
+    v = new Expression (parent, cell, functionText).reduce ();
+    valueType = ValueType.VALUE;
+  }
+
+  @Override
+  public void calculate ()
+  {
+    v.calculate ();
+    if (!v.isValueType (ValueType.VALUE))
+    {
+      valueType = v.getValueType ();
+      return;
+    }
+
+    value = Math.asin (v.getValue ());
+
+    if (Double.isNaN (value))
+      valueType = ValueType.ERROR;
+  }
+}
\ No newline at end of file
diff --git a/src/com/bytezone/diskbrowser/visicalc/Atan.java b/src/com/bytezone/diskbrowser/visicalc/Atan.java
new file mode 100644
index 0000000..f28a376
--- /dev/null
+++ b/src/com/bytezone/diskbrowser/visicalc/Atan.java
@@ -0,0 +1,30 @@
+package com.bytezone.diskbrowser.visicalc;
+
+public class Atan extends Function
+{
+  Value v;
+
+  Atan (Sheet parent, Cell cell, String text)
+  {
+    super (parent, cell, text);
+
+    v = new Expression (parent, cell, functionText).reduce ();
+    valueType = ValueType.VALUE;
+  }
+
+  @Override
+  public void calculate ()
+  {
+    v.calculate ();
+    if (!v.isValueType (ValueType.VALUE))
+    {
+      valueType = v.getValueType ();
+      return;
+    }
+
+    value = Math.atan (v.getValue ());
+
+    if (Double.isNaN (value))
+      valueType = ValueType.ERROR;
+  }
+}
\ No newline at end of file
diff --git a/src/com/bytezone/diskbrowser/visicalc/Choose.java b/src/com/bytezone/diskbrowser/visicalc/Choose.java
index 73cbf52..0704efe 100644
--- a/src/com/bytezone/diskbrowser/visicalc/Choose.java
+++ b/src/com/bytezone/diskbrowser/visicalc/Choose.java
@@ -24,7 +24,14 @@ public class Choose extends Function
   public void calculate ()
   {
     source.calculate ();
-    Address address = range.get ((int) source.getValue () - 1);
+    int index = (int) source.getValue () - 1;
+    if (index < 0 || index >= range.size ())
+    {
+      valueType = ValueType.NA;
+      return;
+    }
+
+    Address address = range.get (index);
     if (address == null)
       valueType = ValueType.NA;
     else
diff --git a/src/com/bytezone/diskbrowser/visicalc/Cos.java b/src/com/bytezone/diskbrowser/visicalc/Cos.java
new file mode 100644
index 0000000..6976652
--- /dev/null
+++ b/src/com/bytezone/diskbrowser/visicalc/Cos.java
@@ -0,0 +1,27 @@
+package com.bytezone.diskbrowser.visicalc;
+
+public class Cos extends Function
+{
+  Value v;
+
+  Cos (Sheet parent, Cell cell, String text)
+  {
+    super (parent, cell, text);
+
+    v = new Expression (parent, cell, functionText).reduce ();
+    valueType = ValueType.VALUE;
+  }
+
+  @Override
+  public void calculate ()
+  {
+    v.calculate ();
+    if (!v.isValueType (ValueType.VALUE))
+    {
+      valueType = v.getValueType ();
+      return;
+    }
+
+    value = Math.cos (v.getValue ());
+  }
+}
\ No newline at end of file
diff --git a/src/com/bytezone/diskbrowser/visicalc/Exp.java b/src/com/bytezone/diskbrowser/visicalc/Exp.java
new file mode 100644
index 0000000..e4469e8
--- /dev/null
+++ b/src/com/bytezone/diskbrowser/visicalc/Exp.java
@@ -0,0 +1,30 @@
+package com.bytezone.diskbrowser.visicalc;
+
+public class Exp extends Function
+{
+  Value v;
+
+  Exp (Sheet parent, Cell cell, String text)
+  {
+    super (parent, cell, text);
+
+    v = new Expression (parent, cell, functionText).reduce ();
+    valueType = ValueType.VALUE;
+  }
+
+  @Override
+  public void calculate ()
+  {
+    v.calculate ();
+    if (!v.isValueType (ValueType.VALUE))
+    {
+      valueType = v.getValueType ();
+      return;
+    }
+
+    value = Math.exp (v.getValue ());
+
+    if (Double.isNaN (value))
+      valueType = ValueType.ERROR;
+  }
+}
\ No newline at end of file
diff --git a/src/com/bytezone/diskbrowser/visicalc/Format.java b/src/com/bytezone/diskbrowser/visicalc/Format.java
index 9ad333b..b5221cc 100644
--- a/src/com/bytezone/diskbrowser/visicalc/Format.java
+++ b/src/com/bytezone/diskbrowser/visicalc/Format.java
@@ -48,6 +48,8 @@ public class Format
           val = val.substring (0, val.length () - 1);
         if (val.startsWith ("0."))
           val = val.substring (1);
+        if (val.startsWith ("-0."))
+          val = "-" + val.substring (2);
 
         if (val.length () > colWidth && val.indexOf ('.') >= 0)
           val = val.substring (0, colWidth);
diff --git a/src/com/bytezone/diskbrowser/visicalc/Function.java b/src/com/bytezone/diskbrowser/visicalc/Function.java
index 735c011..b8984ab 100644
--- a/src/com/bytezone/diskbrowser/visicalc/Function.java
+++ b/src/com/bytezone/diskbrowser/visicalc/Function.java
@@ -42,9 +42,18 @@ abstract class Function extends AbstractValue implements Iterable<Value>
     if (text.startsWith ("@ABS("))
       return new Abs (parent, cell, text);
 
+    if (text.startsWith ("@ACOS("))
+      return new Acos (parent, cell, text);
+
     if (text.startsWith ("@AND("))
       return new And (parent, cell, text);
 
+    if (text.startsWith ("@ASIN("))
+      return new Asin (parent, cell, text);
+
+    if (text.startsWith ("@ATAN("))
+      return new Atan (parent, cell, text);
+
     if (text.startsWith ("@AVERAGE("))
       return new Average (parent, cell, text);
 
@@ -54,9 +63,15 @@ abstract class Function extends AbstractValue implements Iterable<Value>
     if (text.startsWith ("@CHOOSE("))
       return new Choose (parent, cell, text);
 
+    if (text.startsWith ("@COS("))
+      return new Cos (parent, cell, text);
+
     if (text.startsWith ("@ERROR"))
       return new Error (parent, cell, text);
 
+    if (text.startsWith ("@EXP"))
+      return new Exp (parent, cell, text);
+
     if (text.startsWith ("@IF("))
       return new If (parent, cell, text);
 
@@ -69,9 +84,15 @@ abstract class Function extends AbstractValue implements Iterable<Value>
     if (text.startsWith ("@ISNA("))
       return new IsNa (parent, cell, text);
 
+    if (text.startsWith ("@LOG10("))
+      return new Log10 (parent, cell, text);
+
     if (text.startsWith ("@LOOKUP("))
       return new Lookup (parent, cell, text);
 
+    if (text.startsWith ("@LN("))
+      return new Ln (parent, cell, text);
+
     if (text.startsWith ("@MIN("))
       return new Min (parent, cell, text);
 
@@ -90,12 +111,18 @@ abstract class Function extends AbstractValue implements Iterable<Value>
     if (text.startsWith ("@PI"))
       return new Pi (parent, cell, text);
 
+    if (text.startsWith ("@SIN("))
+      return new Sin (parent, cell, text);
+
     if (text.startsWith ("@SUM("))
       return new Sum (parent, cell, text);
 
     if (text.startsWith ("@SQRT("))
       return new Sqrt (parent, cell, text);
 
+    if (text.startsWith ("@TAN("))
+      return new Tan (parent, cell, text);
+
     System.out.printf ("Unknown function: [%s]%n", text);
     return new Error (parent, cell, "@ERROR");
   }
diff --git a/src/com/bytezone/diskbrowser/visicalc/Ln.java b/src/com/bytezone/diskbrowser/visicalc/Ln.java
new file mode 100644
index 0000000..39c420d
--- /dev/null
+++ b/src/com/bytezone/diskbrowser/visicalc/Ln.java
@@ -0,0 +1,27 @@
+package com.bytezone.diskbrowser.visicalc;
+
+public class Ln extends Function
+{
+  Value v;
+
+  Ln (Sheet parent, Cell cell, String text)
+  {
+    super (parent, cell, text);
+
+    v = new Expression (parent, cell, functionText).reduce ();
+    valueType = ValueType.VALUE;
+  }
+
+  @Override
+  public void calculate ()
+  {
+    v.calculate ();
+    if (!v.isValueType (ValueType.VALUE))
+    {
+      valueType = v.getValueType ();
+      return;
+    }
+
+    value = Math.log (v.getValue ());
+  }
+}
\ No newline at end of file
diff --git a/src/com/bytezone/diskbrowser/visicalc/Log10.java b/src/com/bytezone/diskbrowser/visicalc/Log10.java
new file mode 100644
index 0000000..6626aa6
--- /dev/null
+++ b/src/com/bytezone/diskbrowser/visicalc/Log10.java
@@ -0,0 +1,27 @@
+package com.bytezone.diskbrowser.visicalc;
+
+public class Log10 extends Function
+{
+  Value v;
+
+  Log10 (Sheet parent, Cell cell, String text)
+  {
+    super (parent, cell, text);
+
+    v = new Expression (parent, cell, functionText).reduce ();
+    valueType = ValueType.VALUE;
+  }
+
+  @Override
+  public void calculate ()
+  {
+    v.calculate ();
+    if (!v.isValueType (ValueType.VALUE))
+    {
+      valueType = v.getValueType ();
+      return;
+    }
+
+    value = Math.log10 (v.getValue ());
+  }
+}
\ No newline at end of file
diff --git a/src/com/bytezone/diskbrowser/visicalc/Range.java b/src/com/bytezone/diskbrowser/visicalc/Range.java
index 586d11c..8f8dfcd 100644
--- a/src/com/bytezone/diskbrowser/visicalc/Range.java
+++ b/src/com/bytezone/diskbrowser/visicalc/Range.java
@@ -95,7 +95,7 @@ class Range implements Iterable<Address>
 
   public Address get (int index)
   {
-    return range.get (index);
+    return index < 0 || index >= range.size () ? null : range.get (index);
   }
 
   @Override
diff --git a/src/com/bytezone/diskbrowser/visicalc/Sin.java b/src/com/bytezone/diskbrowser/visicalc/Sin.java
new file mode 100644
index 0000000..eb8cd10
--- /dev/null
+++ b/src/com/bytezone/diskbrowser/visicalc/Sin.java
@@ -0,0 +1,27 @@
+package com.bytezone.diskbrowser.visicalc;
+
+public class Sin extends Function
+{
+  Value v;
+
+  Sin (Sheet parent, Cell cell, String text)
+  {
+    super (parent, cell, text);
+
+    v = new Expression (parent, cell, functionText).reduce ();
+    valueType = ValueType.VALUE;
+  }
+
+  @Override
+  public void calculate ()
+  {
+    v.calculate ();
+    if (!v.isValueType (ValueType.VALUE))
+    {
+      valueType = v.getValueType ();
+      return;
+    }
+
+    value = Math.sin (v.getValue ());
+  }
+}
\ No newline at end of file
diff --git a/src/com/bytezone/diskbrowser/visicalc/Tan.java b/src/com/bytezone/diskbrowser/visicalc/Tan.java
new file mode 100644
index 0000000..ff152a3
--- /dev/null
+++ b/src/com/bytezone/diskbrowser/visicalc/Tan.java
@@ -0,0 +1,27 @@
+package com.bytezone.diskbrowser.visicalc;
+
+public class Tan extends Function
+{
+  Value v;
+
+  Tan (Sheet parent, Cell cell, String text)
+  {
+    super (parent, cell, text);
+
+    v = new Expression (parent, cell, functionText).reduce ();
+    valueType = ValueType.VALUE;
+  }
+
+  @Override
+  public void calculate ()
+  {
+    v.calculate ();
+    if (!v.isValueType (ValueType.VALUE))
+    {
+      valueType = v.getValueType ();
+      return;
+    }
+
+    value = Math.tan (v.getValue ());
+  }
+}
\ No newline at end of file