Plain-text math notation to use
To learn mathematics online you have to use some plain-text notation to communicate mathematical symbols, expressions and formulas via computers and Internet. There are various different text notations for math, some are markup and programming languages (like TeX, MathML, etc.), others are just generally accepted varying practices used by math practitioners, educators and students as a common part of their own custom notations. The core of specific notation that we use is such common, generally accepted practice, which means this notation is widely used and easily understood. Our notation differs from similar such notations used by other people only in specific details, and is usually well understood by such people, just as similar notations used by other people are well understood by us.
You can quickly learn our text math notation by the following examples:
| Math symbol, expression or formula | ASCII-only notation | Notation containing non-ASCII Unicode |
|---|---|---|
| a = b a ≠ b | a= b a = b a =b a !=b a != b a!= b | a ≠b a ≠ b a≠ b |
| Equality. Spacing is irrelevant. | ||
| a ≡ a a ≢ 2a | a== a a == a a ==a a !==2a a !== 2a a!== 2a | a≡ a a ≡ a a ≡a a ≢2a a ≢ 2a a≢ 2a |
Identity. Spacing is irrelevant. The == and = are equivalent and mutually substitutive only if equation/identity contains no variables. The same is true for !== and !=. Mnemonic digraph for non-ASCII Unicode: ≡ =3 . |
||
| a = 3 | a= 3 a = 3 a =3 a:= 3 a := 3 a :=3 | a ≔ 3 a≔ 3 a ≔3 |
Assignment. Spacing is irrelevant. The = (i.e. equation) is equivalent to := only if one side of = has no and the other side has exactly 1 variable with non-zero factor. |
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| 4 × 2 4 × b a × 2 a × b | 42
== 4 2
!== 4* 2
== 4 * 2
== 4 *2
== (4) (2)
== (4)(2)
== 4*2
4b
== 4 b
== 4* b
== 4 * b
== 4 *b
== 4*b
// a2 !== // instead...
var a;
a2
== a 2
== a* 2
== a * 2
== a *2
== a*2
// ab !== // instead...
var a, b;
ab
== a b
== a* b
== a * b
== a *b
== a*b |
42 ==
4 2
!== 4× 2
== 4 × 2
== 4 ×2
== (4) (2)
== (4)(2)
== 4×2
4b
== 4 b
== 4× b
== 4 × b
== 4 ×b
== 4×b
// a2 !== // instead...
var a;
a2
== a 2
== a× 2
== a × 2
== a ×2
== a×2
// ab !== // instead...
var a, b;
ab
== a b
== a× b
== a × b
== a ×b
== a×b |
Either use variables unambiguously, or explicitly pre-declare variables with var to avoid ambiguity and allow more compact notation. Do not use latin letter "x" for multiplication, since "x" is typically used as variable name. Mnemonic digraph for non-ASCII Unicode: × *X . |
||
| 4 ÷ 2 | 4/2 | 4 ÷ 2 |
Mnemonic digraph for non-ASCII Unicode: ÷ -: .
| ||
| x2 | x^2 | |
| x^(2 /3) !== x^ 2 /3 == (x^ 2)/3 | ||
| 23x | 2^(3x) !== // NOT identical to next: 2^3x == (2^3)x | |
| x2y3z4 | x^2 y^3 z^4 == (x^2)*(y^3)*(z^4) == x^2 * y^3 * z^4 == x^2y^3z^4 !== x^(2y)^(3z)^4 | |
| Spacing is irrelevant and, in particular, does not imply precedence of operations. | ||
| (1/2)x - 3 == x/2 - 3 !== 1/2x - 3 | ||
| 1/(2x) - 3 !== 1/2x - 3 == x/2 - 3 | ||
| 1/(2x - 3) | ||
| (x - 2)/( 3x^2 + 4x - 5) == (x - 2)/(3*x^2 + 4*x - 5) == (x - 2)/(3 x^2 + 4 x - 5) == (x - 2)/( 3x^2+4 x - 5) | ||
| Spacing is irrelevant and, in particular, does not imply precedence of operations. | ||
| ((x - 2)/3) / ((4x + 5)/6) | ||
| This is exactly the expression that horizontal fraction line in traditional mathematical notation implies. | ||
| (2x^3 - 4)|_0^2 == (2x^3 - 4)|_(x=0)^(x=2) | ||
For expressions containing only one (or no) variable the x= is optional, otherwise it is required.
| ||
| f(x) = 1/x | f(x) == 1/x;
// assuming f and x have not been used/declared as anything else
// except x may have been used/declared as var
// Using function:
f( x)
== f of x // operator applying function to argument(s)
== f x // parenthesis and "of" are optional
// For example:
sin(x)
== sin x; |
|
function f; // optional
x <= 0 => f(x) = sin x;
x > 0 => f(x) = x - x^2;
// Or same using notation of identity restricted to subset of arguments of each piece of the function:
f(x) ==_{x <= 0} sin x;
f(x) ==_{x > 0} x - x^2; |
||
| Piecewise functions. | ||
| f−1(x) | f(x) == 1/x;
f^-1(x) // designates the inverse function
== f^-1 x == 1/x
!== f^(-1)(x) // designates the raising of function to the power of -1
== f(x)^-1
== (f(x))^-1
== 1/f(x) |
|
Only exact literal designation f^-1 implies name of inverse function for function f, anything else is raising f to the power of -1.
| ||
| f (x)−1 | f(x) == 1/x;
f(x)^(-1)
== (f x)^-1
== (f(x))^-1 ==_{x != 0} x
// For any power p:
f( x)^p
== (f( x))^p
== f^p(x)
== f^p x;
// For example:
sin^2 a + cos^2 a
== sin( a)^2 + cos( a)^2
== 1 |
|
| For comparison with designation for inverse function. | ||
| function f, g; (f o g)( x) == (f of g)( x) == f of g of x == f( g( x)) | ||
| Function composition. | ||
| { f(x) = 0, g(x) = 0 } | ||
| Curly system of equations (and/or inequalities). Inequalities can also be present instead of some/all of equations or in addition to equations. Equations and/or inequalities can be any and there can be any number of them. Spacing (including newlines) is irrelevant. | ||
| [ f(x) = 0, g(x) = 0 ] | ||
| Square system of equations (and/or inequalities). Inequalities can also be present instead of some/all of equations or in addition to equations. Equations and/or inequalities can be any and there can be any number of them. Spacing (including newlines) is irrelevant. | ||
| ⌊ x ⌋ | floor(x) | ⌊ x ⌋ |
Mnemonic digraph for non-ASCII Unicode: ⌊ 7< , ⌋ 7> .
| ||
| ⌈ x ⌉ | ceil(x) ceiling(x) | ⌈ x ⌉ |
Mnemonic digraph for non-ASCII Unicode: ⌈ <7 , ⌉ >7 . |
||
(x)^(1/2)
== root2(x)
// Note:
root2(2x)
!== root2 2x # root2 2 has precedence over 2x
== root2(2)*x
// For roots of any higher degree n:
(x)^(1/n)
// or use root3(), root4(), ... |
√(x)
// Note:
√(2x)
!== √ 2x # √2 has precedence over 2x
== √(2)*x
// For roots of 3 and 4 degrees:
∛(x)
∜(x) |
|
Note that only (x)^(1/n) notation allows degree of the root to be a variable. Mnemonic digraph for non-ASCII Unicode: √ RT .
| ||
| ≥ ≤ | >= <= | ≥ ≤ |
Mnemonic digraph for non-ASCII Unicode: ≥ >=, ≤ =< .
| ||
| ≈ | ~ | ≈ |
Approximately equal to (e.g. after rounding, using approximate values of parameters, etc.). Mnemonic digraph for non-ASCII Unicode: ≈ ?= .
| ||
| ± | -+ // but not +- | ± |
| x02 | x_0^2 == x_(0)^2 == (x_(0))^2; i := 0; x_i^2 == x_0^2 == (x_0)^2; | |
| x1,2 | x_(1,2) | |
| xmax3 | //var max; // optional, unless variable `max` has already been declared or used
x_max^3
== (x_max)^3; |
|
| xmin,max | //var min,max; // optional, unless variable `min` or `max` has already been declared or used
x_(min,max) |
|
| Universal way to express any subscripting of variables, functions and operators. | ||
| logb(x) | log(b, x) == log_b(x) | |
| lg(x) = log10(x) | lg(x) == log_10(x) | |
| ln(x) = loge(x) | ln(x) == log_e(x) | |
| |x| | |x| == abs(x) | |
| 0.77... 1.23434... | ||
| ∞ +∞ -∞ | infinity inf +infinity +inf -infinity -inf | ∞ +∞ -∞ |
| f'(x) == df(x)/dx | ||
| f'(x)|_a == df(x)/dx|_a | ||
| Derivative function at a point. | ||
| integral f(x)dx | ∫f(x)dx | |
| integral_a^b f(x)dx | ∫_a^b f(x)dx | |
integral_-infinity^+infinity f(x)dx ==
integral_-inf^+inf f(x)dx |
∫_-∞^+∞ f(x)dx | |
| A ∪ B; A ∩ B; A ⊂ B; A ⊄ B; A ⊆ B; A ⊈ B; a ∈ A; A ∋ a; a ∉ B; A ∌ b; ∅ | set A, B; A unity B; A intersect B; A subset B; A < B; not A subset B ! A < B A subequal B A <= B not A subequal B ! A <= B a in A {a} <= A A has a A => {a} not a in B ! a in B ! {a} <= B not A has b ! A has b ! A => {b} {} | A ∪ B; A ∩ B; A ⊂ B; A ⊄ B; A ⊆ B; A ⊈ B; a ∈ A; A ∋ a; a ∉ B; A ∌ b; ∅ |
| A... ⇒ B...; A... ⇐ B...; A... ⇔ B...; | A... => B...;
if A... then B...; // the same
A... only if B...; // the same
B... <= A...; // the same
B... if A...; // the same
only if B... then A...; // the same
B... => A...;
A... <=> B...;
if and only if A... then B...; // the same
A... if and only if B...; // the same
A... iff B...; // the same
| A... ⇒ B...; A... ⇐ B...; A... ⇔ B...; |
Here A... (and B...) is formulation of some mathematical statement, usually using formal notation described on this page.
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| ∃ ∃! | exists x that A(x)...
exists only one x that A(x)... |
∃ x: A(x)... ∃! x: A(x)... |
Here A(x)... is formulation of some mathematical statement about x, usually using formal notation described on this page, that there exists some value of x that makes A(x)... a true statement.
| ||
| ∀ | for all x: A(x)... |
∀ x: A(x)... |
Here A(x)... is formulation of some mathematical statement about x, usually using formal notation described on this page, that is true statement for all values of x.
| ||
| ∧ ∨ ¬ ~ | A... and B... A... or B... not A... ! A... | |
Here A... (and B...) is formulation of some mathematical statement, usually using formal notation described on this page.
| ||
| π e i | pi
e // base of the natural logarithm function
i // imaginary unit of the complex number |
π e i |
| These names are reserved for corresponding constants and cannot be used as names of variables. | ||
| ∠A + ∠B + ∠C == pi | angle A + angle B + angle C = pi;
angle A, B, C;
A + B + C = pi; |
∠A + ∠B + ∠C == pi |
| a ∥ b a ⊥ b | straight a ll straight b;
straight a, b;
a ll b;
straight a ll plane b;
straight a; plane b;
a ll b;
plane a ll plane b;
plane a, b;
a ll b;
straight a pp straight b;
straight a, b;
a pp b;
straight a pp plane b;
straight a; plane b;
a pp b;
plane a pp plane b;
plane a, b;
a pp b; |
straight a ∥ straight b;
straight a, b;
a ∥ b;
straight a ∥ plane b;
straight a; plane b;
a ∥ b;
plane a ∥ plane b;
plane a, b;
a ∥ b;
straight a ⊥ straight b;
straight a, b;
a ⊥ b;
straight a ⊥ plane b;
straight a; plane b;
a ⊥ b;
plane a ⊥ plane b;
plane a, b;
a ⊥ b; |
| Mnemonics: "paraLLel" and "PerPendicular". Do not use "11" or "||" instead. | ||