最近,在高三听课,发现两个青年教师都在复习课讲了同一道例题,各自采用了不同风格的教法和解法,现将教学过程实录如下:1教学实录题目:在△ABC中,a2=b(b+c),求证:A=2B·教师甲:题目要证明A=2B,即证cosA=cos2B,接下来用a,b,c表示cosA,cos2B,由余弦定理知,cosA=b2+c2-a22bc=b2+c2- Recently, during the third year of class, it was found that the two young teachers all talked about the same example in the review class. They each adopted different styles of teaching methods and solutions. The teaching process is now recorded as follows: 1 Teaching Record Title: In ABC, a2 =b(b+c), Proof: A=2B • Teacher A: The topic is to prove A=2B, that is, proof cosA=cos2B, then use a, b, c for cosA, cos2B, which is known from the cosine theorem, cosA= B2+c2-a22bc=b2+c2-