There are rectangle PQRS and a right-angled triangle ABC whose angle B is right as shown in a figure.
Triangle ABC is rotated for the surroundings of rectangle PQRS as follows.
The point A is at point P and point B is on the side PS at first.
① Triangle ABC is clockwise rotated around point B until the point C and the point S overlaps.
② Next, triangle ABC is clockwise rotated around point C until the point A and the point R overlaps.
③ Next, triangle ABC is clockwise rotated around point A until the point B comes on the side QR.
Triangle ABC is rotated for the surroundings of rectangle PQRS as follows.
The point A is at point P and point B is on the side PS at first.
① Triangle ABC is clockwise rotated around point B until the point C and the point S overlaps.
② Next, triangle ABC is clockwise rotated around point C until the point A and the point R overlaps.
③ Next, triangle ABC is clockwise rotated around point A until the point B comes on the side QR.