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原题如图1,已知AB∥EF,求证:∠BCF=∠B+∠F.(人教版初中《几何》第一册第119页第7题)
The original question is shown in Fig. 1, known as AB∥EF, and verification: ∠BCF=∠B+∠F. (Pattern junior high school “Geometry” Volume 1 page 119, item 7)