MathDB
angle wanted, parallelogram, tangents to circle, equal angles related

Source: 2016 Portugal p4

October 10, 2020
geometryparallelogramTangentsequal anglesangles

Problem Statement

Let [ABCD][ABCD] be a parallelogram with AB<BCAB <BC and let E,FE, F be points on the circle that passes through A,BA, B and CC such that DEDE and DFDF are tangents to this circle. Knowing that ∠ADE=∠CDF\angle ADE = \angle CDF , determine ∠ABC\angle ABC. https://cdn.artofproblemsolving.com/attachments/5/e/4140b92730e9d382df49ac05ca4e8ba48332dc.png
Back to ProblemsView on AoPS