This is all I know,
= equality x = y means x and y represent the same thing or value. 1 + 1 = 2
is equal to; equals
everywhere
â
<>
!= inequation x â y means that x and y do not represent the same thing or value. 1 â 2
is not equal to; does not equal
everywhere
<
>
âª
â« strict inequality x < y means x is less than y.
x > y means x is greater than y.
x ⪠y means x is much less than y.
x â« y means x is much greater than y. 3 < 4
5 > 4.
0.003 ⪠1000000
is less than, is greater than, is much less than, is much greater than
order theory
â¤
⥠inequality x ⤠y means x is less than or equal to y.
x ⥠y means x is greater than or equal to y. 3 ⤠4 and 5 ⤠5
5 ⥠4 and 5 ⥠5
is less than or equal to, is greater than or equal to
order theory
â proportionality y â x means that y = kx for some constant k. if y = 2x, then y â x
is proportional to
everywhere
+ addition 4 + 6 means the sum of 4 and 6. 2 + 7 = 9
plus
arithmetic
disjoint union A1 + A2 means the disjoint union of sets A1 and A2. A1 = {1, 2, 3, 4} ⧠A2 = {2, 4, 5, 7} â
A1 + A2 = {(1,1), (2,1), (3,1), (4,1), (2,2), (4,2), (5,2), (7,2)}
the disjoint union of ... and ...
set theory
â subtraction 9 â 4 means the subtraction of 4 from 9. 8 â 3 = 5
minus
arithmetic
negative sign â3 means the negative of the number 3. â(â5) = 5
negative ; minus
arithmetic
set-theoretic complement A â B means the set that contains all the elements of A that are not in B. {1,2,4} â {1,3,4} = {2}
minus; without
set theory
à multiplication 3 à 4 means the multiplication of 3 by 4. 7 à 8 = 56
times
arithmetic
Cartesian product XÃY means the set of all ordered pairs with the first element of each pair selected from X and the second element selected from Y. {1,2} Ã {3,4} = {(1,3),(1,4),(2,3),(2,4)}
the Cartesian product of ... and ...; the direct product of ... and ...
set theory
cross product u à v means the cross product of vectors u and v (1,2,5) à (3,4,â1) =
(â22, 16, â 2)
cross
vector algebra
· multiplication 3 · 4 means the multiplication of 3 by 4. 7 · 8 = 56
times
arithmetic
dot product u · v means the dot product of vectors u and v (1,2,5) · (3,4,â1) = 6
dot
vector algebra
÷
⁄ division 6 ÷ 3 or 6 ⁄ 3 means the division of 6 by 3. 2 ÷ 4 = .5
12 ⁄ 4 = 3
divided by
arithmetic
±
â plus-minus 6 ± 3 means 6 + 3 or 6 - 3.
6 ± 3 â 5 means 6 + 3 - 5 or 6 - 3 + 5. 6 ± 3 = 9 or 3
6 ± 3 â 5 = 4 or 8
plus-minus; plus-or-minus
minus-plus; minus-or-plus
arithmetic
â square root âx means the positive number whose square is x. â4 = 2
the principal square root of; square root
real numbers
complex square root if z = r exp(iÏ) is represented in polar coordinates with -Ï < Ï â¤ Ï, then âz = âr exp(iÏ/2). â(-1) = i
the complex square root of; square root
complex numbers
| | absolute value |x| means the distance in the real line (or the complex plane) between x and zero. |3| = 3, |-5| = |5|
|i| = 1, |3+4i| = 5
absolute value of
numbers
Euclidean distance |x-y| means the Euclidean distance between x and y. If x=(1,1), and y=(4,5), then |x-y| = â((1-4)2+(1-5)2)=5
Euclidean distance between; Euclidean norm of
Geometry
| divides A single vertical bar is used to denote divisibility.
a|b means a divides b. Since 15 = 3Ã5, it is true that 3|15 and 5|15.
divides
Number Theory
! factorial n! is the product 1 Ã 2Ã ... Ã n. 4! = 1 Ã 2 Ã 3 Ã 4 = 24
factorial
combinatorics
~ probability distribution X ~ D, means the random variable X has the probability distribution D. X ~ N(0,1), the standard normal distribution
has distribution
statistics
â
â
â material implication A â B means if A is true then B is also true; if A is false then nothing is said about B.
â may mean the same as â, or it may have the meaning for functions given below.
â may mean the same as â, or it may have the meaning for superset given below. x = 2 â x2 = 4 is true, but x2 = 4 â x = 2 is in general false (since x could be â2).
implies; if .. then
propositional logic
â
â material equivalence A â B means A is true if B is true and A is false if B is false. x + 5 = y +2 â x + 3 = y
if and only if; iff
propositional logic
¬
Ë logical negation The statement ¬A is true if and only if A is false.
A slash placed through another operator is the same as "¬" placed in front. ¬(¬A) â A
x â y â ¬(x = y)
not
propositional logic
⧠logical conjunction or meet in a lattice The statement A ⧠B is true if A and B are both true; else it is false.
For functions A(x) and B(x), A(x) ⧠B(x) is used to mean min(A(x), B(x)). n < 4 ⧠n >2 â n = 3 when n is a natural number.
and; min
propositional logic, lattice theory
⨠logical disjunction or join in a lattice The statement A ⨠B is true if A or B (or both) are true; if both are false, the statement is false.
For functions A(x) and B(x), A(x) ⨠B(x) is used to mean max(A(x), B(x)). n ⥠4 ⨠n ⤠2 â n â 3 when n is a natural number.
or; max
propositional logic, lattice theory
â
â» exclusive or The statement A â B is true when either A or B, but not both, are true. A â» B means the same. (¬A) â A is always true, A â A is always false.
xor
propositional logic, Boolean algebra
direct sum The direct sum is a special way of combining several one modules into one general module (the symbol â is used, â» is only for logic).
Most commonly, for vector spaces U, V, and W, the following consequence is used:
U = V â W â (U = V + W) ⧠(V â© W = â
)
direct sum of
Abstract algebra
â universal quantification â x: P(x) means P(x) is true for all x. â n â N: n2 ⥠n.
for all; for any; for each
predicate logic
â existential quantification â x: P(x) means there is at least one x such that P(x) is true. â n â N: n is even.
there exists
predicate logic
â! uniqueness quantification â! x: P(x) means there is exactly one x such that P(x) is true. â! n â N: n + 5 = 2n.
there exists exactly one
predicate logic
:=
â¡
:â definition x := y or x â¡ y means x is defined to be another name for y (but note that â¡ can also mean other things, such as congruence).
P :â Q means P is defined to be logically equivalent to Q. cosh x := (1/2)(exp x + exp (âx))
A XOR B :â (A ⨠B) ⧠¬(A ⧠B)
is defined as
everywhere
â
congruence â³ABC â
â³DEF means triangle ABC is congruent to triangle DEF.
is congruent to
geometry
{ , } set brackets {a,b,c} means the set consisting of a, b, and c. N = {0, 1, 2, ...}
the set of ...
set theory
{ : }
{ | } set builder notation {x : P(x)} means the set of all x for which P(x) is true. {x | P(x)} is the same as {x : P(x)}. {n â N : n2 < 20} = {0, 1, 2, 3, 4}
the set of ... such that ...
set theory
â
{} empty set â
means the set with no elements. {} means the same. {n â N : 1 < n2 < 4} = â
the empty set
set theory
â
â set membership a â S means a is an element of the set S; a â S means a is not an element of S. (1/2)â1 â N
2â1 â N
is an element of; is not an element of
everywhere, set theory
â
â subset (subset) A â B means every element of A is also element of B.
(proper subset) A â B means A â B but A â B. A â© B â A; Q â R
is a subset of
set theory
â
â superset A â B means every element of B is also element of A.
A â B means A â B but A â B. A ⪠B â B; R â Q
is a superset of
set theory
⪠set-theoretic union (exclusive) A ⪠B means the set that contains all the elements from A, or all the elements from B, but not both.
"A or B, but not both".
(inclusive) A ⪠B means the set that contains all the elements from A, or all the elements from B, or all the elements from both A and B.
"A or B or both". A â B â A ⪠B = B (inclusive)
the union of ... and ...; union
set theory
â© set-theoretic intersection A â© B means the set that contains all those elements that A and B have in common. {x â R : x2 = 1} â© N = {1}
intersected with; intersect
set theory
Î symmetric difference AÎB means the set of elements in exactly one of A or B. {1,5,6,8}Î {2,5,8} = {1,2,6}
symmetric difference
set theory
â set-theoretic complement A â B means the set that contains all those elements of A that are not in B. {1,2,3,4} â {3,4,5,6} = {1,2}
minus; without
set theory
( ) function application f(x) means the value of the function f at the element x. If f(x) := x2, then f(3) = 32 = 9.
of
set theory
precedence grouping Perform the operations inside the parentheses first. (8/4)/2 = 2/2 = 1, but 8/(4/2) = 8/2 = 4.
parentheses
everywhere
f:XâY function arrow f: X â Y means the function f maps the set X into the set Y. Let f: Z â N be defined by f(x) := x2.
from ... to
set theory
o function composition fog is the function, such that (fog)(x) = f(g(x)). if f(x) := 2x, and g(x) := x + 3, then (fog)(x) = 2(x + 3).
composed with
set theory
N
â natural numbers N means {0, 1, 2, 3, ...}, but see the article on natural numbers for a different convention. {|a| : a â Z} = N
N
numbers
Z
⤠integers Z means {..., â3, â2, â1, 0, 1, 2, 3, ...}. {a, -a : a â N} = Z
Z
numbers
Q
â rational numbers Q means {p/q : p,q â Z, q â 0}. 3.14 â Q
Ï â Q
Q
numbers
R
â real numbers R means the set of real numbers. Ï â R
â(â1) â R
R
numbers
C
â complex numbers C means {a + bi : a,b â R}. i = â(â1) â C
C
numbers
arbitrary constant C can be any number, most likely unknown; usually occurs when calculating antiderivatives. if f(x) = 6x² + 4x, then F(x) = 2x³ + 2x² + C
C
integral calculus
â infinity â is an element of the extended number line that is greater than all real numbers; it often occurs in limits. limxâ0 1/|x| = â
infinity
numbers
Ï pi Ï is the ratio of a circle's circumference to its diameter. Its value is 3.1415.... A = Ïr² is the area of a circle with radius r
pi
Euclidean geometry
|| || norm ||x|| is the norm of the element x of a normed vector space. ||x+y|| ⤠||x|| + ||y||
norm of; length of
linear algebra
â summation means a1 + a2 + ... + an.
= 12 + 22 + 32 + 42
= 1 + 4 + 9 + 16 = 30
sum over ... from ... to ... of
arithmetic
â product means a1a2···an.
= (1+2)(2+2)(3+2)(4+2)
= 3 Ã 4 Ã 5 Ã 6 = 360
product over ... from ... to ... of
arithmetic
Cartesian product means the set of all (n+1)-tuples
(y0,...,yn).
the Cartesian product of; the direct product of
set theory
â coproduct
coproduct over ... from ... to ... of
category theory
′ derivative f ′(x) is the derivative of the function f at the point x, i.e., the slope of the tangent to f at x. If f(x) := x2, then f ′(x) = 2x
... prime; derivative of ...
calculus
â« indefinite integral or antiderivative â« f(x) dx means a function whose derivative is f. â«x2 dx = x3/3 + C
indefinite integral of ...;; the antiderivative of ...
calculus
definite integral â«ab f(x) dx means the signed area between the x-axis and the graph of the function f between x = a and x = b. â«0b x2 dx = b3/3;
integral from ... to ... of ... with respect to
calculus
â gradient âf (x1, …, xn) is the vector of partial derivatives (âf / âx1, …, âf / âxn). If f (x,y,z) := 3xy + z², then âf = (3y, 3x, 2z)
del, nabla, gradient of
calculus
â partial derivative With f (x1, …, xn), âf/âxi is the derivative of f with respect to xi, with all other variables kept constant. If f(x,y) := x2y, then âf/âx = 2xy
partial derivative of
calculus
boundary âM means the boundary of M â{x : ||x|| ⤠2} = {x : ||x|| = 2}
boundary of
topology
⥠perpendicular x ⥠y means x is perpendicular to y; or more generally x is orthogonal to y. If l ⥠m and m ⥠n then l || n.
is perpendicular to
geometry
bottom element x = ⥠means x is the smallest element. âx : x ⧠⥠= â¥
the bottom element
lattice theory
|| parallel x || y means x is parallel to y. If l || m and m ⥠n then l ⥠n.
is parallel to
geometry
⧠entailment A ⧠B means the sentence A entails the sentence B, that is every model in which A is true, B is also true. A ⧠A ⨠¬A
entails
model theory
⢠inference x ⢠y means y is derived from x. A â B ⢠¬B â ¬A
infers or is derived from
propositional logic, predicate logic
â
normal subgroup N â
G means that N is a normal subgroup of group G. Z(G) â
G
is a normal subgroup of
group theory
/ quotient group G/H means the quotient of group G modulo its subgroup H. {0, a, 2a, b, b+a, b+2a} / {0, b} = {{0, b}, {a, b+a}, {2a, b+2a}}
mod
group theory
quotient set A/~ means the set of all ~ equivalence classes in A.
set theory
â isomorphism G â H means that group G is isomorphic to group H Q / {1, â1} â V,
where Q is the quaternion group and V is the Klein four-group.
is isomorphic to
group theory
approximately equal x â y means x is approximately equal to y Ï â 3.14159
is approximately equal to
everywhere
<,> inner product means the inner product between x and y, as defined in an inner product space. The standard inner product between two vectors x = (2, 3) and y = (-1, 5) is:
= 2Ã-1 + 3Ã5 = 13
inner product of
vector algebra
â tensor product V â U means the tensor product of V and U. {1, 2, 3, 4} â {1,1,2} =
{{1, 2, 3, 4}, {1, 2, 3, 4}, {2, 4, 6, 8}}
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2006-09-24 03:26:09
·
answer #2
·
answered by Anonymous
·
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