🐛 [Bug]: Multiple logic and UI edge cases in Ultra Pro Calculator

[Sanjhivvarshan-b-s]

📝 Description

While testing the "Ultra Pro Calculator" on the web app, I found several logic and UI bugs. Specifically:

1. The "Error" State Trap: Appending numbers to an "Error" state breaks the calculator.
2. Scientific Function Crash: Pressing sin, cos, etc., on an incomplete expression (like 5+) throws an evaluation error.
3. Radian vs Degree: Trigonometry functions calculate in radians instead of degrees.
4. Visual Symbol Mismatch: The UI displays * and / instead of × and ÷.
   and more

🔄 Steps to Reproduce

For the "Error" trap:

1. Go to the Web App and open the Ultra Pro Calculator.
2. Enter an invalid calculation (e.g., 5 ÷ 0 = or + =) to trigger the "Error" screen.
3. Press the number 5.
4. See Error5 on the display.

For the Radian bug:

1. Clear the calculator.
2. Press 9, 0, and then sin.
3. See incorrect output.

For the Visual bug:

1. Press 5, ×, 5.
2. See 5*5 on the display instead of 5×5.

🎯 Expected Behavior

• If the screen displays "Error", pressing a new number should clear the screen first.
• Pressing sin after typing 90 should output 1 (calculating in degrees, not radians).
• Pressing the multiplication or division buttons should visually display × and ÷ on the screen.

❌ Actual Behavior / Error Logs

• The calculator concatenates strings to the error message (e.g., "Error5").
• sin(90) outputs 0.8939966636005579 (calculated in radians).
• The display shows programmer symbols (*, /) instead of standard math symbols.
• Passing incomplete expressions (like 5+) to scientific functions throws a silent JavaScript runtime error and fails to update the UI.

💻 Environment

• OS: Any (Browser-based)
• Python Version: N/A (JavaScript Web App)

• File Name: calculator.js

---

• I am a registered GSSoC 2026 contributor.
• I want to be assigned to fix this issue.

[github-actions]

⚠️ Important Contribution Guideline

Please do not open a Pull Request without being assigned to this issue first.

Please do not open a Pull Request without being assigned to this issue first.

How to proceed:

1. Comment on this issue to express interest
2. Wait for maintainers to assign you to the issue
3. Once assigned, you can start working on the PR
4. Include the assignment in your PR checklist

Thank you for helping us maintain a smooth workflow! 🙏

[steam-bell-92]

@Sanjhivvarshan-b-s assigned