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The nabla is a triangular symbol resembling an inverted Greek delta: [1] or ∇. The name comes, by reason of the symbol's shape, from the Hellenistic Greek word νάβλα for a Phoenician harp, [2] [3] and was suggested by the encyclopedist William Robertson Smith in an 1870 letter to Peter Guthrie Tait.
The nabla symbol, written as an upside-down triangle and pronounced "del", denotes the vector differential operator. When a coordinate system is used in which the basis vectors are not functions of position, the gradient is given by the vector [ a ] whose components are the partial derivatives of f {\displaystyle f} at p {\displaystyle p} . [ 2 ]
The glyph of the up tack appears as an upside-down tee symbol, and as such is sometimes called eet (the word "tee" in reverse). [citation needed] Tee plays a complementary or dual role in many of these theories. The similar-looking perpendicular symbol ( , \perp in LaTeX, U+27C2 in Unicode) is a binary relation symbol used to represent:
An intriguing catchphrase typography upside down invites the reader to rotate the magazine, in which the first names "Michael" or "Peter" are transformed into "Nathalie" or "Alice". [107] [108] In 2015 iSmart's logo on one of its travel chargers went viral because the brand's name turned out to be a natural ambigram that read "+Jews!" upside down.
Redundant, but sometimes used for emphasizing that a number is positive, specially when other numbers in the context are or may be negative; for example, +2. 3. Sometimes used instead of for a disjoint union of sets. − 1. Denotes subtraction and is read as minus; for example, 3 – 2. 2.
Del, or nabla, is an operator used in mathematics (particularly in vector calculus) as a vector differential operator, usually represented by the nabla symbol ∇. When applied to a function defined on a one-dimensional domain, it denotes the standard derivative of the function as defined in calculus .
In this table, parentheses mark letters that stand in for themselves or for another. For instance, a rotated 'b' would be a 'q', and indeed some physical typefaces didn't bother with distinct sorts for lowercase b vs. q, d vs. p, or n vs. u; while a rotated 's' or 'z' would be itself.
The solvable version of the problem. Here, cups A and C are upside down, and cup B is upright. The three cups problem, also known as the three cup challenge and other variants, is a mathematical puzzle that, in its most common form, cannot be solved. In the beginning position of the problem, one cup is upside-down and the other two are right ...