MathDB
convex quadrilateral with angles and sides in 2 arithmetic sequences

Source: 2021 Dürer Math Competition Finals Day2 E+16 https://artofproblemsolving.com/community/c2749870_

January 9, 2022
geometryanglesarithmetic sequence

Problem Statement

The angles of a convex quadrilateral form an arithmetic sequence in clockwise order, and its side lengths also form an arithmetic sequence (but not necessarily in clockwise order). If the quadrilateral is not a square, and its shortest side has length 11, then its perimeter is a+b4a + \sqrt{b}4, where a a and bb are positive integers. What is the value of a+ba + b?