How to Use Math Symbols in gnome-terminal

HOLD CTRL+SHIFT + U + CODEPOINT. That's it.

For e.g. CTRL + SHIFT + U + 2200 will output ∀ After typing CTRL + SHIFT + U,
when the terminal identifies that what follows is unicode, you might leave the
keypresses and just type the codepoint.

∀ U2200
∁ U2201
∂ U2202
∃ U2203
∄ U2204
∅ U2205
∆ U2206
  U2207
  U2208
∉ U2209
∊ U220A