180 degree rotations

if you download the powerpoint here the rotations are animated

rotate 180 about 1

rotate this (image) shape 180 about 2

rotate about another point 3

through 180 to end in the position shown above

students could produce their own examples

what do students notice if they connect together the four centres of rotation?

consider the effect of two 180 degree rotations about different centres

two rotations through 180 degrees seems to be a translation

what relationship is there between the translation vector and the two centres of enlargement?



a reason for this, approached vectorially: