MathDB
spiral by similar triangles

Source: 2018 Ecuador Juniors (OMEC) L2 p4

October 25, 2022
geometrysimilar trianglessimilarity

Problem Statement

Given a positive integer n>1n > 1 and an angle α<90o\alpha < 90^o, Jaime draws a spiral OP0P1...PnOP_0P_1...P_n of the following form (the figure shows the first steps): \bullet First draw a triangle OP0P1OP_0P_1 with OP0=1OP_0 = 1, P1OP0=α\angle P_1OP_0 = \alpha and P1P0O=90oP_1P_0O = 90^o \bullet then for every integer 1in1 \le i \le n draw the point Pi+1P_{i+1} so that Pi+1OPi=α\angle P_{i+1}OP_i = \alpha, Pi+1PiO=90o\angle P_{i+1}P_iO = 90^o and Pi1P_{i-1} and Pi+1P_{i+1} are in different half-planes with respect to the line OPiOP_i https://cdn.artofproblemsolving.com/attachments/f/2/aa3913989dac1cf04f2b42b5d630b2e096dcb6.png a) If n=6n = 6 and α=30o\alpha = 30^o, find the length of P0PnP_0P_n. b) If n=2018n = 2018 and α=45o\alpha= 45^o, find the length of P0PnP_0P_n.