2014 AMC 12B Problem 25
Below is the professionally curated solution for Problem 25 of the 2014 AMC 12B, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2014 AMC 12B solutions, or check the answer key.
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Difficulty rating: 2890
25.
What is the sum of all positive real solutions to the equation
Solution:
Let Dividing by and using the equation simplifies to
Both cosines must equal or both equal so and are integers of the same parity. Since is even, both must be even, so with a positive odd divisor of giving
Each such gives so the sum of solutions is
Thus, the correct answer is D.
Problem 25 in Other Years
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