diff --git a/lib/calculator.dart b/lib/calculator.dart
index 190d132..20cfedf 100644
--- a/lib/calculator.dart
+++ b/lib/calculator.dart
@@ -1,5 +1,5 @@
 // === 在 abstract class Expr 中添加声明 ===
-import 'dart:math' show sqrt, cos, sin, tan, pow;
+import 'dart:math' show sqrt, cos, sin, tan, pow, log, exp, asin, acos, atan;
 import 'parser.dart';
 
 abstract class Expr {
@@ -621,8 +621,9 @@ class PowExpr extends Expr {
     // 1^x = 1
     if (l is IntExpr && l.value == 1) return IntExpr(1);
     // 0^x = 0 (for x != 0)
-    if (l is IntExpr && l.value == 0 && !(r is IntExpr && r.value == 0))
+    if (l is IntExpr && l.value == 0 && !(r is IntExpr && r.value == 0)) {
       return IntExpr(0);
+    }
 
     // If both are numbers, compute
     if (l is IntExpr && r is IntExpr) {
@@ -669,6 +670,192 @@ class PowExpr extends Expr {
   }
 }
 
+// === LogExpr ===
+class LogExpr extends Expr {
+  final Expr inner;
+  LogExpr(this.inner);
+
+  @override
+  Expr simplify() => LogExpr(inner.simplify());
+
+  @override
+  Expr evaluate() {
+    var i = inner.evaluate();
+    if (i is IntExpr) {
+      return DoubleExpr(log(i.value.toDouble()));
+    }
+    if (i is FractionExpr) {
+      return DoubleExpr(log(i.numerator / i.denominator));
+    }
+    if (i is DoubleExpr) {
+      return DoubleExpr(log(i.value));
+    }
+    return LogExpr(i);
+  }
+
+  @override
+  Expr substitute(String varName, Expr value) =>
+      LogExpr(inner.substitute(varName, value));
+
+  @override
+  String toString() => "log($inner)";
+}
+
+// === ExpExpr ===
+class ExpExpr extends Expr {
+  final Expr inner;
+  ExpExpr(this.inner);
+
+  @override
+  Expr simplify() => ExpExpr(inner.simplify());
+
+  @override
+  Expr evaluate() {
+    var i = inner.evaluate();
+    if (i is IntExpr) {
+      return DoubleExpr(exp(i.value.toDouble()));
+    }
+    if (i is FractionExpr) {
+      return DoubleExpr(exp(i.numerator / i.denominator));
+    }
+    if (i is DoubleExpr) {
+      return DoubleExpr(exp(i.value));
+    }
+    return ExpExpr(i);
+  }
+
+  @override
+  Expr substitute(String varName, Expr value) =>
+      ExpExpr(inner.substitute(varName, value));
+
+  @override
+  String toString() => "exp($inner)";
+}
+
+// === AsinExpr ===
+class AsinExpr extends Expr {
+  final Expr inner;
+  AsinExpr(this.inner);
+
+  @override
+  Expr simplify() => AsinExpr(inner.simplify());
+
+  @override
+  Expr evaluate() {
+    var i = inner.evaluate();
+    if (i is IntExpr) {
+      return DoubleExpr(asin(i.value.toDouble()));
+    }
+    if (i is FractionExpr) {
+      return DoubleExpr(asin(i.numerator / i.denominator));
+    }
+    if (i is DoubleExpr) {
+      return DoubleExpr(asin(i.value));
+    }
+    return AsinExpr(i);
+  }
+
+  @override
+  Expr substitute(String varName, Expr value) =>
+      AsinExpr(inner.substitute(varName, value));
+
+  @override
+  String toString() => "asin($inner)";
+}
+
+// === AcosExpr ===
+class AcosExpr extends Expr {
+  final Expr inner;
+  AcosExpr(this.inner);
+
+  @override
+  Expr simplify() => AcosExpr(inner.simplify());
+
+  @override
+  Expr evaluate() {
+    var i = inner.evaluate();
+    if (i is IntExpr) {
+      return DoubleExpr(acos(i.value.toDouble()));
+    }
+    if (i is FractionExpr) {
+      return DoubleExpr(acos(i.numerator / i.denominator));
+    }
+    if (i is DoubleExpr) {
+      return DoubleExpr(acos(i.value));
+    }
+    return AcosExpr(i);
+  }
+
+  @override
+  Expr substitute(String varName, Expr value) =>
+      AcosExpr(inner.substitute(varName, value));
+
+  @override
+  String toString() => "acos($inner)";
+}
+
+// === AtanExpr ===
+class AtanExpr extends Expr {
+  final Expr inner;
+  AtanExpr(this.inner);
+
+  @override
+  Expr simplify() => AtanExpr(inner.simplify());
+
+  @override
+  Expr evaluate() {
+    var i = inner.evaluate();
+    if (i is IntExpr) {
+      return DoubleExpr(atan(i.value.toDouble()));
+    }
+    if (i is FractionExpr) {
+      return DoubleExpr(atan(i.numerator / i.denominator));
+    }
+    if (i is DoubleExpr) {
+      return DoubleExpr(atan(i.value));
+    }
+    return AtanExpr(i);
+  }
+
+  @override
+  Expr substitute(String varName, Expr value) =>
+      AtanExpr(inner.substitute(varName, value));
+
+  @override
+  String toString() => "atan($inner)";
+}
+
+// === AbsExpr ===
+class AbsExpr extends Expr {
+  final Expr inner;
+  AbsExpr(this.inner);
+
+  @override
+  Expr simplify() => AbsExpr(inner.simplify());
+
+  @override
+  Expr evaluate() {
+    var i = inner.evaluate();
+    if (i is IntExpr) {
+      return IntExpr(i.value.abs());
+    }
+    if (i is FractionExpr) {
+      return FractionExpr(i.numerator.abs(), i.denominator);
+    }
+    if (i is DoubleExpr) {
+      return DoubleExpr(i.value.abs());
+    }
+    return AbsExpr(i);
+  }
+
+  @override
+  Expr substitute(String varName, Expr value) =>
+      AbsExpr(inner.substitute(varName, value));
+
+  @override
+  String toString() => "|$inner|";
+}
+
 // === 辅助：识别 a * sqrt(X) 形式 ===
 class _SqrtTerm {
   final int coef;
diff --git a/lib/parser.dart b/lib/parser.dart
index bd7b9c0..7cb2fce 100644
--- a/lib/parser.dart
+++ b/lib/parser.dart
@@ -62,76 +62,121 @@ class Parser {
 
   Expr parseAtom() {
     skipSpaces();
+    bool negative = false;
+    if (current == '-') {
+      negative = true;
+      eat();
+      skipSpaces();
+    }
+    Expr expr;
     if (current == '(') {
       eat();
-      var expr = parse();
+      expr = parse();
       if (current != ')') throw Exception("缺少 )");
       eat();
-      return expr;
-    }
-
-    if (input.startsWith("sqrt", pos)) {
+    } else if (input.startsWith("sqrt", pos)) {
       pos += 4;
       if (current != '(') throw Exception("sqrt 缺少 (");
       eat();
       var inner = parse();
       if (current != ')') throw Exception("sqrt 缺少 )");
       eat();
-      return SqrtExpr(inner);
-    }
-
-    if (input.startsWith("cos", pos)) {
+      expr = SqrtExpr(inner);
+    } else if (input.startsWith("cos", pos)) {
       pos += 3;
       if (current != '(') throw Exception("cos 缺少 (");
       eat();
       var inner = parse();
       if (current != ')') throw Exception("cos 缺少 )");
       eat();
-      return CosExpr(inner);
-    }
-
-    if (input.startsWith("sin", pos)) {
+      expr = CosExpr(inner);
+    } else if (input.startsWith("sin", pos)) {
       pos += 3;
       if (current != '(') throw Exception("sin 缺少 (");
       eat();
       var inner = parse();
       if (current != ')') throw Exception("sin 缺少 )");
       eat();
-      return SinExpr(inner);
-    }
-
-    if (input.startsWith("tan", pos)) {
+      expr = SinExpr(inner);
+    } else if (input.startsWith("tan", pos)) {
       pos += 3;
       if (current != '(') throw Exception("tan 缺少 (");
       eat();
       var inner = parse();
       if (current != ')') throw Exception("tan 缺少 )");
       eat();
-      return TanExpr(inner);
-    }
-
-    // 解析变量 (单个字母)
-    if (RegExp(r'[a-zA-Z]').hasMatch(current)) {
+      expr = TanExpr(inner);
+    } else if (input.startsWith("log", pos)) {
+      pos += 3;
+      if (current != '(') throw Exception("log 缺少 (");
+      eat();
+      var inner = parse();
+      if (current != ')') throw Exception("log 缺少 )");
+      eat();
+      expr = LogExpr(inner);
+    } else if (input.startsWith("exp", pos)) {
+      pos += 3;
+      if (current != '(') throw Exception("exp 缺少 (");
+      eat();
+      var inner = parse();
+      if (current != ')') throw Exception("exp 缺少 )");
+      eat();
+      expr = ExpExpr(inner);
+    } else if (input.startsWith("asin", pos)) {
+      pos += 4;
+      if (current != '(') throw Exception("asin 缺少 (");
+      eat();
+      var inner = parse();
+      if (current != ')') throw Exception("asin 缺少 )");
+      eat();
+      expr = AsinExpr(inner);
+    } else if (input.startsWith("acos", pos)) {
+      pos += 4;
+      if (current != '(') throw Exception("acos 缺少 (");
+      eat();
+      var inner = parse();
+      if (current != ')') throw Exception("acos 缺少 )");
+      eat();
+      expr = AcosExpr(inner);
+    } else if (input.startsWith("atan", pos)) {
+      pos += 4;
+      if (current != '(') throw Exception("atan 缺少 (");
+      eat();
+      var inner = parse();
+      if (current != ')') throw Exception("atan 缺少 )");
+      eat();
+      expr = AtanExpr(inner);
+    } else if (current == '|') {
+      eat();
+      var inner = parse();
+      if (current != '|') throw Exception("abs 缺少 |");
+      eat();
+      expr = AbsExpr(inner);
+    } else if (RegExp(r'[a-zA-Z]').hasMatch(current)) {
       var varName = current;
       eat();
-      return VarExpr(varName);
-    }
-
-    // 解析数字 (整数或小数)
-    var buf = '';
-    bool hasDot = false;
-    while (!isEnd &&
-        (RegExp(r'\d').hasMatch(current) || (!hasDot && current == '.'))) {
-      if (current == '.') hasDot = true;
-      buf += current;
-      eat();
-    }
-    if (buf.isEmpty) throw Exception("无法解析: $current");
-    if (hasDot) {
-      return DoubleExpr(double.parse(buf));
+      expr = VarExpr(varName);
     } else {
-      return IntExpr(int.parse(buf));
+      // 解析数字 (整数或小数)
+      var buf = '';
+      bool hasDot = false;
+      while (!isEnd &&
+          (RegExp(r'\d').hasMatch(current) || (!hasDot && current == '.'))) {
+        if (current == '.') hasDot = true;
+        buf += current;
+        eat();
+      }
+      if (buf.isEmpty) throw Exception("无法解析: $current");
+      if (hasDot) {
+        expr = DoubleExpr(double.parse(buf));
+      } else {
+        expr = IntExpr(int.parse(buf));
+      }
     }
+    if (negative) {
+      expr = SubExpr(IntExpr(0), expr);
+    }
+    return expr;
   }
 }
 
diff --git a/lib/solver.dart b/lib/solver.dart
index 53da5d4..199336f 100644
--- a/lib/solver.dart
+++ b/lib/solver.dart
@@ -1,4 +1,5 @@
 import 'dart:math';
+import 'package:flutter/foundation.dart';
 import 'package:rational/rational.dart';
 import 'models/calculation_step.dart';
 import 'calculator.dart';
@@ -553,26 +554,26 @@ ${b1}y &= ${c1 - a1 * x.toDouble()}
       if (factorMulMatch != null) {
         final factor1 = factorMulMatch.group(1)!;
         final factor2 = factorMulMatch.group(2)!;
-        print('Expanding: ($factor1) * ($factor2)');
+        debugPrint('Expanding: ($factor1) * ($factor2)');
 
         final coeffs1 = _parsePolynomial(factor1);
         final coeffs2 = _parsePolynomial(factor2);
-        print('Coeffs1: $coeffs1, Coeffs2: $coeffs2');
+        debugPrint('Coeffs1: $coeffs1, Coeffs2: $coeffs2');
 
         final a = coeffs1[1] ?? 0;
         final b = coeffs1[0] ?? 0;
         final c = coeffs2[1] ?? 0;
         final d = coeffs2[0] ?? 0;
-        print('a=$a, b=$b, c=$c, d=$d');
+        debugPrint('a=$a, b=$b, c=$c, d=$d');
 
         final newA = a * c;
         final newB = a * d + b * c;
         final newC = b * d;
-        print('newA=$newA, newB=$newB, newC=$newC');
+        debugPrint('newA=$newA, newB=$newB, newC=$newC');
 
         final expanded =
             '${newA}x^2${newB >= 0 ? '+' : ''}${newB}x${newC >= 0 ? '+' : ''}$newC';
-        print('Expanded result: $expanded');
+        debugPrint('Expanded result: $expanded');
 
         result = result.replaceFirst(factorMulMatch.group(0)!, expanded);
         iterationCount++;
@@ -1033,7 +1034,7 @@ ${b1}y &= ${c1 - a1 * x.toDouble()}
 
         if (simplifiedB == 0) {
           // Just the sqrt part with correct sign
-          return isPlus ? '$sqrtExpr' : '-$sqrtExpr';
+          return isPlus ? sqrtExpr : '-$sqrtExpr';
         } else if (simplifiedB == 1) {
           // +1 * sqrt part
           return isPlus ? '1 + $sqrtExpr' : '1 - $sqrtExpr';
@@ -1052,11 +1053,11 @@ ${b1}y &= ${c1 - a1 * x.toDouble()}
         }
       } else {
         // Cannot simplify, use fraction form
-        final bStr = b > 0 ? '${bInt}' : '(${bInt})';
+        final bStr = b > 0 ? '$bInt' : '($bInt)';
         final signStr = isPlus ? '+' : '-';
         final numerator = b > 0
             ? '-$bStr $signStr $sqrtExpr'
-            : '(${bInt}) $signStr $sqrtExpr';
+            : '($bInt) $signStr $sqrtExpr';
 
         if (denominator == 2) {
           return '\\frac{$numerator}{2}';
diff --git a/test_expand.dart b/test_expand.dart
deleted file mode 100644
index ad93f5f..0000000
--- a/test_expand.dart
+++ /dev/null
@@ -1,21 +0,0 @@
-import 'lib/solver.dart';
-
-void main() {
-  final solver = SolverService();
-
-  // Test the problematic case
-  final input = '(x+8)(x+1)=-12';
-  print('Input: $input');
-
-  try {
-    final result = solver.solve(input);
-    print('Result: ${result.finalAnswer}');
-    print('Steps:');
-    for (final step in result.steps) {
-      print('Step ${step.stepNumber}: ${step.title}');
-      print('  Formula: ${step.formula}');
-    }
-  } catch (e) {
-    print('Error: $e');
-  }
-}