Each jump is carried out four times in a cycle,
Both quadrilateral ABP4P3 and quadrilateral ABP3P2 are isosceles trapezoid.
Jump 15 times to P4,
A is the extension line from AM⊥P4P 1 to m, from P 1M=4-3= 1,
AP 1=6,∴AM=√35,
P4M=6+ 1=7,
∴ap4&; sup2=35+49=84,
AP4=2√2 1。