Dash Insert drop-down menu. Dash The dash is a punctuation mark that is similar in appearance to and , but differs from these symbols in both length and height. The most common versions of the dash are the en dash (–), equal to half the height of the font; the em dash (—), twice as long as the en dash; and the horizontal bar (―), whose length varies across typefaces. Historically, the names of en dash and em dash were loosely related to the width of a lower-case "n" and upper-case "M", respectively, in commonly used typefaces. Usage varies both within
General Leibniz rule General Leibniz rule In calculus, the general Leibniz rule, named after Gottfried Wilhelm Leibniz, generalizes the product rule (which is also known as "Leibniz's rule"). It states that if formula_1 and formula_2 are formula_3-times differentiable functions, then the product formula_4 is also formula_3-times differentiable and its formula_3th derivative is given by where formula_8 is the binomial coefficient and formula_9 This can be proved by using the product rule and mathematical induction. If, for example, , the rule gives an expression for the second derivative of a product of two functions: The formula can be generalized to the product of "m"