diff --git a/pom.xml b/pom.xml
index 51aebdc2..5732e6ad 100644
--- a/pom.xml
+++ b/pom.xml
@@ -65,6 +65,15 @@
 			</exclusions>
 		</dependency>
 
+		<dependency>
+			<groupId>achartengine</groupId>
+			<artifactId>achartengine</artifactId>
+			<version>0.7.0</version>
+			<scope>system</scope>
+			<systemPath>${additionalLibs}/achartengine-0.7.0.jar</systemPath>
+		</dependency>
+
+
 		<dependency>
 			<groupId>com.intellij</groupId>
 			<artifactId>annotations</artifactId>
diff --git a/src/main/java/org/solovyev/android/calculator/model/CalculatorEngine.java b/src/main/java/org/solovyev/android/calculator/model/CalculatorEngine.java
index 97bb1925..06dd60cd 100644
--- a/src/main/java/org/solovyev/android/calculator/model/CalculatorEngine.java
+++ b/src/main/java/org/solovyev/android/calculator/model/CalculatorEngine.java
@@ -188,6 +188,9 @@ public enum CalculatorEngine {
 					} catch (ArithmeticException e) {
 						//System.out.println(e.getMessage());
 						exception.setObject(new ParseException(e.getMessage(), e));
+					} catch (StackOverflowError e) {
+						//System.out.println(StringUtils.fromStackTrace(e.getStackTrace()));
+						exception.setObject(new ParseException(e.getMessage(), e));
 					} catch (jscl.text.ParseException e) {
 						//System.out.println(e.getMessage());
 						exception.setObject(new ParseException(e.getMessage(), e));
diff --git a/src/misc/src/achartengine-0.7.0.jar b/src/misc/src/achartengine-0.7.0.jar
new file mode 100644
index 00000000..aec45ffc
Binary files /dev/null and b/src/misc/src/achartengine-0.7.0.jar differ
diff --git a/src/test/java/org/solovyev/android/calculator/model/CalculatorEngineTest.java b/src/test/java/org/solovyev/android/calculator/model/CalculatorEngineTest.java
index dc081551..b928e64a 100644
--- a/src/test/java/org/solovyev/android/calculator/model/CalculatorEngineTest.java
+++ b/src/test/java/org/solovyev/android/calculator/model/CalculatorEngineTest.java
@@ -157,12 +157,7 @@ public class CalculatorEngineTest {
 		Assert.assertEquals("3.957", cm.evaluate(JsclOperation.numeric, "ln(8)lg(8)+ln(8)").getResult());
 
 		Assert.assertEquals("0", cm.evaluate(JsclOperation.numeric, "((((((0))))))").getResult());
-		try {
-			Assert.assertEquals("0", cm.evaluate(JsclOperation.numeric, "((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((0))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))").getResult());
-			fail();
-		} catch (ParseException e) {
-			// ok
-		}
+		Assert.assertEquals("0", cm.evaluate(JsclOperation.numeric, "((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((((0))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))").getResult());
 
 
 		/*	Assert.assertEquals("0.524", cm.evaluate(JsclOperation.numeric, "30°").getResult());
@@ -232,11 +227,7 @@ public class CalculatorEngineTest {
 		} catch (ParseException e) {
 		}
 
-		try {
-			Assert.assertEquals("0.739", cm.evaluate(JsclOperation.numeric, "cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(1))))))))))))))))))))))))))))))))))))").getResult());
-			Assert.fail();
-		} catch (ParseException e) {
-		}
+		Assert.assertEquals("0.739", cm.evaluate(JsclOperation.numeric, "cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(cos(1))))))))))))))))))))))))))))))))))))").getResult());
 
 		CalculatorEngine.instance.getVarsRegister().add(new Var.Builder("si", 5d));
 		Assert.assertEquals("5", cm.evaluate(JsclOperation.numeric, "si").getResult());
@@ -312,10 +303,17 @@ public class CalculatorEngineTest {
 		} catch (ParseException e) {
 
 		}
+
 		Assert.assertEquals("0.017", cm.evaluate(JsclOperation.numeric, "1°").getResult());
 		Assert.assertEquals("0.349", cm.evaluate(JsclOperation.numeric, "20.0°").getResult());
 		Assert.assertEquals("0.5", cm.evaluate(JsclOperation.numeric, "sin(30°)").getResult());
 		Assert.assertEquals("0.524", cm.evaluate(JsclOperation.numeric, "asin(sin(30°))").getResult());
+		try {
+			Assert.assertEquals("∂(cos(t), t, t,1°)", cm.evaluate(JsclOperation.numeric, "∂(cos(t),t,t,1°)").getResult());
+			fail();
+		} catch (ParseException e) {
+		}
 
+		Assert.assertEquals("∂(cos(t), t, t,1°)", cm.evaluate(JsclOperation.simplify, "∂(cos(t),t,t,1°)").getResult());
 	}
 }