if the first one is a clockwise rotation by 90% about the origin then what must be the second transformation?

Answer 1

a clockwise transformation by rotating 90 degrees converts (x,y) into (y,-x)

to get back to (x,y) requires a 270 degree clockwise transformation

or a 90 degree counterclockwise transformation

for example, consider a unit circle and a point on the circle such as (sqr2/2, sqr2/2)

a 90 degree clockwise transformation leads to (sqr2/2, -sqr2/2)

or take a point (sqr3/4, sqr7/4). rotate it clockwise 90 degrees to get (sqr7/4, -sqr3/4)