Problem
1087: Tangent Circles, Parallel, 15 Degrees, Angle
Level: High School, College, Math Education The figure below shows
the circles of centers O and Q tangent at A. BC is tangent to circle Q at C and parallel to OA.
Prove that angle COB = 15 degrees.
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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