Problem 296: Intersecting Circles, Chord, Radius, Angle,
Perpendicular.
Level: High School, College, SAT Prep. In the figure, the circles O and Q intersect at A and B. C is a point on
circle O. Lines AC and BC meet circle Q at points D and E, respectively. Prove that
lines OC and DE are perpendicular.
Geometry problem solving
Geometry problem solving is one of the most challenging skills for students to learn. When a problem requires auxiliary construction, the difficulty of the problem increases drastically, perhaps because deciding which construction to make is an illstructured problem. By “construction,” we mean adding geometric figures (points, lines, planes) to a problem figure that wasn’t mentioned as "given."

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