三角形ABC的三边分别为a,b,c,边BC上的中线记为m,用于弦定理证明,m=1/2根号2(b^2+c^2)-a^2由余弦定理,cos B=(a^2+c^2-b^2)/2ac,m^2=AD^2=c^2+(a/2)^2-2*c*a/2*cos B,把第一个式子代入第二个式子我怎么带进去得到
来源:学生作业帮助网 编辑:作业帮 时间:2024/07/18 06:18:57
![三角形ABC的三边分别为a,b,c,边BC上的中线记为m,用于弦定理证明,m=1/2根号2(b^2+c^2)-a^2由余弦定理,cos B=(a^2+c^2-b^2)/2ac,m^2=AD^2=c^2+(a/2)^2-2*c*a/2*cos B,把第一个式子代入第二个式子我怎么带进去得到](/uploads/image/z/6913545-33-5.jpg?t=%E4%B8%89%E8%A7%92%E5%BD%A2ABC%E7%9A%84%E4%B8%89%E8%BE%B9%E5%88%86%E5%88%AB%E4%B8%BAa%2Cb%2Cc%2C%E8%BE%B9BC%E4%B8%8A%E7%9A%84%E4%B8%AD%E7%BA%BF%E8%AE%B0%E4%B8%BAm%2C%E7%94%A8%E4%BA%8E%E5%BC%A6%E5%AE%9A%E7%90%86%E8%AF%81%E6%98%8E%2Cm%3D1%2F2%E6%A0%B9%E5%8F%B72%EF%BC%88b%5E2%2Bc%5E2%29-a%5E2%E7%94%B1%E4%BD%99%E5%BC%A6%E5%AE%9A%E7%90%86%2Ccos+B%3D%28a%5E2%2Bc%5E2-b%5E2%29%2F2ac%2Cm%5E2%3DAD%5E2%3Dc%5E2%2B%28a%2F2%29%5E2-2%2Ac%2Aa%2F2%2Acos+B%2C%E6%8A%8A%E7%AC%AC%E4%B8%80%E4%B8%AA%E5%BC%8F%E5%AD%90%E4%BB%A3%E5%85%A5%E7%AC%AC%E4%BA%8C%E4%B8%AA%E5%BC%8F%E5%AD%90%E6%88%91%E6%80%8E%E4%B9%88%E5%B8%A6%E8%BF%9B%E5%8E%BB%E5%BE%97%E5%88%B0)
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