这些你都知道吗?以后给老外作报告的时候可千万别再"the eq ation is like this...", "the val e 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 eq ivalent to q  p and q are eq ivalent 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 s bset of b a⊃b a contains b  b is a s bset of a a∩b a cap b  a meet b  a intersection b a∪b a c p b  a join b  a nion b ab a min s b  the diference between a and b a×b a cross b  the cartesian prod ct of a and b 3. real n mbers x+1 x pl s one x-1 x min s one x±1 x pl s or min s one xy xy  x m ltiplied by y (x-y)(x+y) x min s y, x pl s y = the eq als sign x=5 x eq als 5  x is eq al to 5 x≠5 x (is) not eq al to 5 x≡y x is eq ivalent to (or identical with) y xy x is greater than y x≥y x is greater than or eq al to y xx is less than y x≤y x is less than or eq al to y 0zero is less than x is less than 1 0≤x≤1 zero is less than or eq al to x is less than or eq al to 1 |x| mod x  mod l s x x2 x sq ared  x (raised) to the power 2 x3 x c bed x4 x to the fo rth  x to the power 4 xn x to the nth  x to the power n x (−n) x to the (power) min s n x的平方根(sq are) root x  the sq are root of x x的三次根c be root (of) x x的四次根fo rth root (of) x x的n次根nth root (of) x (x+y)2 x pl s y all sq ared n!