1. + : Plus sign 2. - : Minus sign 3. x : Multiplication sign 4. ÷ : Division sign 5. = : Equal sign 6. < : Less than sign 7. > : Greater than sign 8. ≤ : Less than or equal to sign 9. ≥ : Greater than or equal to sign 10. √ : Square root symbol 11. π : Pi symbol 12. ∞ : Infinity symbol 13. % : Percent symbol 14. ∑ : Summation symbol 15. ∫ : Integral symbol 16. ∆ : Delta symbol 17. θ : Theta symbol 18. ∠ : Angle symbol 19. ∝ : Proportional to symbol 20. ∩ : Intersection symbol