it seems that no-one else wants to make a fool of themselves, so here goes!
1:rotate 60 degrees around point C
2:do (x,y) —> (x,0) for all points
This assumes that C is in the same position in both pics.
naturally this is hardly a rigid transformation, but it is linear.
Pity we lost a dimension in the process!

it seems that no-one else wants to make a fool of themselves, so here goes!

1:rotate 60 degrees around point C

2:do (x,y) —> (x,0) for all points

This assumes that C is in the same position in both pics.

naturally this is hardly a rigid transformation, but it is linear.

Pity we lost a dimension in the process!

The other one is

1:rotate as before

2:rotate 90 degrees around the AD line

3:look down from above