Update app.py

app.py

@@ -416,7 +416,7 @@ STRICT REQUIREMENTS:
    - Format numerical results using evalf() for decimal
 9. When writing SymPy code to verify solutions:
    - Start with essential imports: from sympy import * 
-   - Or use specific imports as needed: from sympy import Symbol, solve, limit, Abs, integrate, Function, diff, sin, cos
+   - Or use specific imports as needed: from sympy import Symbol, symbols, solve, limit, Abs, integrate, Function, diff, sin, cos
    - DO NOT use NumPy, SciPy, or other libraries
    - For numerical integration, use integrate() instead of scipy.integrate.quad()
    - For any numerical computations, use native SymPy functions