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Honduran National MO (OHM) Intermediate Problem 2

Source: 2021 OHM Intermediate P2

November 21, 2021
algebra

Problem Statement

Let a,b,c,da,b,c,d be real numbers such that a2+b2=1,c2+d2=1a^2+b^2=1,c^2+d^2=1 and ac+bd=0ac+bd=0. Determine all possible values of ab+cdab+cd.