求一立体几何题解答正三棱锥,P-ABC,PA=8,AB=4,过A的截面交PB,PC于D,E.求三角形ADE周长最小值.(将三棱椎侧面展开,连直线,用三角函数求长度,不过需要求等腰三角行顶角的三倍的角的余弦值,麻烦,
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![求一立体几何题解答正三棱锥,P-ABC,PA=8,AB=4,过A的截面交PB,PC于D,E.求三角形ADE周长最小值.(将三棱椎侧面展开,连直线,用三角函数求长度,不过需要求等腰三角行顶角的三倍的角的余弦值,麻烦,](/uploads/image/z/4062212-44-2.jpg?t=%E6%B1%82%E4%B8%80%E7%AB%8B%E4%BD%93%E5%87%A0%E4%BD%95%E9%A2%98%E8%A7%A3%E7%AD%94%E6%AD%A3%E4%B8%89%E6%A3%B1%E9%94%A5%2CP-ABC%2CPA%3D8%2CAB%3D4%2C%E8%BF%87A%E7%9A%84%E6%88%AA%E9%9D%A2%E4%BA%A4PB%2CPC%E4%BA%8ED%2CE.%E6%B1%82%E4%B8%89%E8%A7%92%E5%BD%A2ADE%E5%91%A8%E9%95%BF%E6%9C%80%E5%B0%8F%E5%80%BC.%EF%BC%88%E5%B0%86%E4%B8%89%E6%A3%B1%E6%A4%8E%E4%BE%A7%E9%9D%A2%E5%B1%95%E5%BC%80%2C%E8%BF%9E%E7%9B%B4%E7%BA%BF%2C%E7%94%A8%E4%B8%89%E8%A7%92%E5%87%BD%E6%95%B0%E6%B1%82%E9%95%BF%E5%BA%A6%2C%E4%B8%8D%E8%BF%87%E9%9C%80%E8%A6%81%E6%B1%82%E7%AD%89%E8%85%B0%E4%B8%89%E8%A7%92%E8%A1%8C%E9%A1%B6%E8%A7%92%E7%9A%84%E4%B8%89%E5%80%8D%E7%9A%84%E8%A7%92%E7%9A%84%E4%BD%99%E5%BC%A6%E5%80%BC%2C%E9%BA%BB%E7%83%A6%2C)
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