Update app.py

app.py

@@ -855,6 +855,8 @@ make sure the question is CLEAR about what regions you intend to be included in
    - Verify the point lies on the curve
    - State whether it's a regular point or special point (cusp, corner, etc.)
 
+16. Be careful with trigonometric expressions involving powers
+   - Example: solving sin^2(x)=cos(x) can be solved as 1-cos^2(x)=cos(x)
 
 """