# pound 井号
/ slash, divide, oblique 斜线,斜杠,除号
\ backslash, sometimes escape 反斜线转义符,有时表示转义符或续行符
∫ the integral of …的积分
@ at
underscore是下划线
四分之三 Three-quarters
对x求导The derivative of x
对x求二阶导数Find the second derivative of x