∥ ∠ ? ? ≡ ≌ △

2 algebraic symbols

∝ ∧ ∨ ~ ∫ ≠ ≤ ≥ ≈ ∞ ∶

3 operation symbol ×√.

4 symbol set ∩ Ⅰ

5 Special symbol ∑ π (π)

6 reasoning symbol

| One |? ? △ ∠ ∩ ∪ ≠ ≡ ≥ ≤ ⅰ ?