Question

a<=>b
does it mean
b<=>a?

Answer 1

And also
a=>b
does it mean
b=>a?

Answer 2

I don't know about

a<=>b

but often times

a=>b

means a is equal to or greater than b

Answer 3

\[a\iff b\] is the same as
\[b\iff a\]

Answer 4

since arrow goes both directions. however,
\[a\implies b\] is not the same as \[b\implies a\]

Answer 5

a simple example will suffice. suppose "a" is "the figure is a square" and "b" is "the figure is a rectangle"
then
\[a\implies b\] because any square is a rectangle, but
\[b\implies a\]is false because not all rectangles are squares

Answer 6

the second is exactly like ,the same to firt just ,,viceversa" --- so inversed