First, the radian is different.

Capitals are two straight lines, and lowercase has a little curvature. There is no need to distinguish in the calculation, and the unknown x can be expressed in the junior high school.

Second, it's different outside.

X' can be omitted, so it is a formal writing method of mathematics, which is very useful for writing math problems. He should pay attention to distinguish it from the Chinese pinyin' X'. Chinese pinyin should not be prominent, and mathematics should generally be prominent.

Extended data:

The Latin letter X comes from the pronunciation of the Greek letter χ, not directly from ξ (a letter inspired by Samekh). However, the Greek letter χ may come from the second variant of the Phoenician letter samekh.

According to textual research, the Phoenician alphabet is mainly based on the pictures and characters of ancient Egypt. In ancient Egypt, "A" was a picture of a bull's head; "B" is a picture representing "home" or "yard"; "C" and "G" are pictures representing "a ruler"; "D" is a picture of a door leaf.

"e" is a picture of "a person who raises his hand and shouts"; "F", "V" and "Y" are pictures representing "stick" or "stick"; "H" is a picture representing "a piece of hemp coil"; "I" is a picture representing "open hands"; "K" is a picture representing "palm"; "M" is a diagram representing "water"; "n" is a diagram representing "snake"; "O" is a picture representing "eyes"; "P" is a graph representing "mouth"; "Q" is a picture representing "rope loop".

"R" is a picture representing "human head"; "S" and "X" are pictures representing "hilly land" or "fish"; "T" is a graph representing "vertical and horizontal"; "Z" is a picture, meaning "pry" or "arrow". In the 2nd century BC, these 23 letters were included in the Latin alphabet.

Later, in order to facilitate carving and writing, and to distinguish the vowel "V" from the consonant "V", the lower part of the original "V" was changed into a circle and named as the vowel "U"; When two "V" are connected, they form the consonant "W", and this "W" has appeared for 1 1 century.

Later, people changed the "I" slightly and created another consonant letter "J". In this way, the original 23 letters plus "U", "W" and "J" form a 26-letter alphabet.

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