If HG and a and b belong to G, then

 

(1)

(2) aH = H if and only if

(3) aH = bH or aHbH = Ø

(4) aH = bH if and only if

(5) |aH| = |bH|

(6) aH = Ha if and only if H = aHa-1

(7) aHG if and only if