All Russian 2014 Grade 10 Day 2 - Problem 4

TIMESTAMPS: 00:00 INTRO 45 - 90/150 - 270 Take 10/15 00:37 Reading and understanding the problem 01:20 Solving geometry of this type 01:50 First questions to ask ourselves 02:55 Drawing the first diagram and asking first question 04:22 Looking at connecting R 06:25 Some angles 07:15 CONCYCLIC QUADS ! 09:40 What we have thus far 10:50 The next steps with angles 13:04 R, P, Q connection intuition 17:40 The main logic behind idea and idea 20:40 Finishing with the idea 22:57 The mind=blown moment 23:51 Reflecting on the problem 26:02 Thanks for problem solving :)