Tan90 degrees was originally a mathematical formula. According to trigonometric function, Tan90 = Sin90/Cos90 = 1/0. Therefore, Tan90 does not exist, so netizens often use Tan90 to ridicule the meaning of non-existence.
The extended meaning is to express the meaning that something can't exist or happen with the meaning of tan90 degrees.
Reference example:
"Non-existent" Yan characters have been popular for some time.
At first, tan90 came from the mantra of a betta anchor. An anchor of betta fish will say "does not exist, will beat me, does not exist!" " When the enemy hero tries to kill him, he will also say "does not exist" and then be hit in the face in an instant. This mantra became popular and became an expression pack.