Having a brain fart about permutations

[semidevil]

ok, very very simple, but I cannot for the life of me remember this.

why is (12)(13) = 132? I can't work it out...

 

[Tide]

Why? Because it's not!

P.S. I recommend BEANO for your condition. :-)

 

[shmoe]

Mmm, your permutations are applied right to left? I think Tide goes the other way, left to right...not that there's anything wrong with that of course.

If in doubt, apply your lhs and rhs permutations to 123 and see what heppens. Both sides should give the same permutation.

 

[Tide]

If you start with 3 elements, say (A, B, C) then (12) places A in the second position but (13) does not affect the element in the second position so the result must start with (12... Yes, this is "left-right" which I believe is the convention.

 

[shmoe]

IYes, this is "left-right" which I believe is the convention.

I don't think it's as conventional as other conventions though.

All the texts I have handy work right to left, though a few mention that left to right is also common. I'd wager semidevil's going right to left since it works for his problem.

 

[Tide]

Shmoe,

I suppose some conventions are more conventional than others!

In any case, semidevil should be following the "conventions" prescribed in his class and he might inform us which one they are using if he/she expects further assistance.