2020 AIME I Problem 15
Below is the professionally curated solution for Problem 15 of the 2020 AIME I, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2020 AIME I solutions, or check the answer key.
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Difficulty rating: 3500
15.
Let be an acute triangle with circumcircle and orthocenter Suppose the tangent to the circumcircle of at intersects at points and with and The area of can be written as where and are positive integers, and is not divisible by the square of any prime. Find
Solution:
Reflecting over line lands on so the circumcircle of is the reflection of over Take the circumcenter as the origin, so that as vectors. If is the midpoint of then so the reflected center is Tangency at means is perpendicular to the radius from to which is the vector the chord is perpendicular to
Place so that is horizontal at height with The half-chord length is and give with From so Then giving
Now so and whence The distance from to line (through perpendicular to ) is using Hence and
Problem 15 in Other Years
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