Let < QPR = x Let length side small square be a and large square be b If PA'A is a straight line AB/PC=A¢B¢/PB¢ In triangle PD'C' PC¢ = D¢C¢cotx = a cotx

Therefore PB¢ = a + a cotx

Therefore A¢B¢/PB¢=

a a + a cotx

=

1 1 + cot

In triangle PDC PC = DC cotx = b cotx

Therefore PB = b + b cotx

Therefore AB/PB =

b b + b cotx

=

1 1 + cotx

AB/PC=A¢B¢/PB¢ Therefore PAA' is a straight line