Subjects geometry, number theory

Cogwheel Fibonacci 109495

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Cogwheel Fibonacci 109495


1. **Problem Statement:** We need to find the minimum value of the product $p \times q \times r \times s$ where: - Starting from a 9-digit Fibonacci number displayed by the cogs, - $p$ clicks lead to a triple forming a Primitive Pythagorean Triple, - $q$ further clicks lead to a triangle with a 60° angle, - $r$ further clicks lead to a triangle with integer area, - $s$ further clicks lead back to a 9-digit Fibonacci number. 2. **Understanding the Setup:** - The cogs display triples of numbers concatenated as 9-digit Fibonacci numbers. - Rotating the blue cog clockwise moves the red cogs anticlockwise. - Each click corresponds to moving to the next triple in the sequence. 3. **Key Mathematical Concepts:** - **Primitive Pythagorean Triple:** A triple $(a,b,c)$ with $a^2 + b^2 = c^2$ and $ ext{gcd}(a,b,c) = 1$. - **Triangle with 60° angle:** Using the Law of Cosines, for sides $(x,y,z)$, if angle opposite $z$ is 60°, then $z^2 = x^2 + y^2 - xy$. - **Triangle with integer area:** Using Heron's formula, area $= \sqrt{s(s-a)(s-b)(s-c)}$ where $s=\frac{a+b+c}{2}$ must be an integer. 4. **Approach:** - Identify all 9-digit Fibonacci numbers that appear on the cogs. - For each, simulate clicks $p, q, r, s$ to find triples satisfying the conditions. - Calculate $p \times q \times r \times s$ and find the minimum. 5. **Final Answer:** - The minimum product $p \times q \times r \times s$ is the value to enter on the Ritangle login page. (Note: The problem is complex and requires computational simulation of cog rotations and checking conditions for triples. The exact numeric answer depends on the cog data and sequences.)