Question

How do I rotate a triangle 270 degrees clockwise about the origin?

Answer 1

270 degrees is 90+90+90 or three fourths of the way around.

If you have a drawing of the triangle, you can redraw each corner by imagining it rotated around 3/4 of the way around a circle, going clockwise, then connect the corners.

If you have a hard time imagining, think of a clock with hands... 3/4 of the way around is like moving a time forward by 45 minutes. So a point of a triangle at the 5 minute mark would rotate around to the 50 minute mark.