Question

What is a letter or symbol in algebra?

Answer 1

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 = t1 - t0
∆ discriminant Δ = b2 - 4ac
∑ sigma summation - sum of all values in range of series ∑ xi= x1+x2+...+xn
∑∑ sigma double summation
∏ capital pi product - product of all values in range of series ∏ xi=x1∙x2∙...∙xn
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