Symbol | Symbol Name | Meaning / definition | Example |
---|---|---|---|
x | x variable | unknown value to find | when 2x = 4, then x = 2 |
≡ | equivalence | identical to | |
≜ | equal by definition | equal by definition | |
:= | equal by definition | equal by definition | |
~ | approximately equal | weak approximation | 11 ~ 10 |
≈ | approximately equal | approximation | sin(0.01) ≈ 0.01 |
∝ | proportional to | proportional to | y ∝ x when y = kx, k constant |
∞ | lemniscate | infinity symbol | |
≪ | much less than | much less than | 1 ≪ 1000000 |
≫ | much greater than | much greater than | 1000000 ≫ 1 |
( ) | parentheses | calculate expression inside first | 2 * (3+5) = 16 |
[ ] | brackets | calculate expression inside first | [(1+2)*(1+5)] = 18 |
{ } | braces | set | |
⌊x⌋ | floor brackets | rounds number to lower integer | ⌊4.3⌋ = 4 |
⌈x⌉ | ceiling brackets | rounds number to upper integer | ⌈4.3⌉ = 5 |
x! | exclamation mark | factorial | 4! = 1*2*3*4 = 24 |
| x | | single vertical bar | absolute value | | -5 | = 5 |
f (x) | function of x | maps values of x to f(x) | f (x) = 3x+5 |
(f ∘ g) | function composition | (f ∘ g) (x) = f (g(x)) | f (x)=3x,g(x)=x-1 ⇒(f ∘ g)(x)=3(x-1) |
(a,b) | open interval | (a,b) = {x | a < x < b} | x∈ (2,6) |
[a,b] | closed interval | [a,b] = {x | a ≤ x ≤ b} | x ∈ [2,6] |
∆ | delta | change / difference | ∆t = t_{1 }– t_{0} |
∆ | discriminant | Δ = b^{2} – 4ac | |
∑ | sigma | summation – sum of all values in range of series | ∑ x_{i}= x_{1}+x_{2}+…+x_{n} |
∑∑ | sigma | double summation | |
∏ | capital pi | product – product of all values in range of series | ∏ x_{i}=x_{1}∙x_{2}∙…∙x_{n} |
e | e constant / Euler’s number | e = 2.718281828… | e = lim (1+1/x)^{x} , x→∞ |
γ | Euler-Mascheroni constant | γ = 0.527721566… | |
φ | golden ratio | golden ratio constant | |
π | pi constant | π = 3.141592654…is the ratio between the circumference and diameter of a circle | c = π·d = 2·π·r |