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这些你都知道吗？以后给老外作报告的时候可千万别再“The equation is like this…”, “The value is like this…”

有些公式不好写，能看出来什么意思就行了。

**1.Logic**

∃there exist

∀for all

p⇒q p implies q / if p, then q

p⇔q p if and only if q /p is equivalent to q / p and q are equivalent

**2.Sets**

x∈A x belongs to A / x is an element (or a member) of A

x∉A x does not belong to A / x is not an element (or a member) of A

A⊂B A is contained in B / A is a subset of B

A⊃B A contains B / B is a subset of A

A∩B A cap B / A meet B / A intersection B

A∪B A cup B / A join B / A union B

AB A minus B / the diference between A and B

A×B A cross B / the cartesian product of A and B

**3. Real numbers**

x+1 x plus one

x-1 x minus one

x±1 x plus or minus one

xy xy / x multiplied by y

(x-y)(x+y) x minus y, x plus y

= the equals sign

x=5 x equals 5 / x is equal to 5

x≠5 x (is) not equal to 5

x≡y x is equivalent to (or identical with) y

x>y x is greater than y

x≥y x is greater than or equal to y

x<y x is less than y

x≤y x is less than or equal to y

0<x<1 zero is less than x is less than 1

0≤x≤1 zero is less than or equal to x is less than or equal to 1

|x| mod x / modulus x

x^{2 }x squared / x (raised) to the power 2

x^{3 }x cubed

x^{4} x to the fourth / x to the power 4

x^{n} x to the nth / x to the power n

x^{ (−n) }x to the (power) minus n

x的平方根(square) root x / the square root of x

x的三次根cube root (of) x

x的四次根fourth root (of) x

x的n次根nth root (of) x

(x+y)^{2} x plus y all squared

n! n factorial

x^x hat

x¯ x bar

x˜ x tilde

x_{i} xi / x subscript i / x suffix i / x sub i

∑(i=1~n) a_{i} the sum from i equals one to n a_{i} / the sum as i runs from 1 to n of the a_{i}

**4. Linear algebra**

‖x‖the norm (or modulus) of x

OA^{→}OA / vector OA

OA¯ OA / the length of the segment OA

A^{T} A transpose / the transpose of A

A^{−1} A inverse / the inverse of A

**5. Functions**

f(x) fx / f of x / the function f of x

f:S→T a function f from S to T

x→y x maps to y / x is sent (or mapped) to y

f’(x) f prime x / f dash x / the (first) derivative of f with respect to x

f”(x) f double-prime x / f double-dash x / the second derivative of f with respect to x

f”’(x) triple-prime x / f triple-dash x / the third derivative of f with respect to x

f (4) (x) f four x / the fourth derivative of f with respect to x

∂f/∂x_{1} the partial (derivative) of f with respect to x1

∂^{2}f/∂x_{1}^{2} the second partial (derivative) of f with respect to x1

∫_{0}^{∞} the integral from zero to infinity

lim_{x}_{→}_{0}the limit as x approaches zero

lim_{x}_{→}_{0+}the limit as x approaches zero from above

lim_{x}_{→}_{0−}the limit as x approaches zero from below

log_{e}y log y to the base e / log to the base e of y / natural log (of) y

lny log y to the base e / log to the base e of y / natural log (of) y

from:renren.com