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PUMaC 2013 · 团队赛 · 第 12 题

PUMaC 2013 — Team Round — Problem 12

专题
Discrete Math / 离散数学
难度
L3
来源
PUMaC

题目详情

  1. Let D be a point on the side BC of 4 ABC . If AB = 8, AC = 7, BD = 2 and CD = 1, find AD . 5 4
解析
  1. Let D be a point on the side BC of 4 ABC . If AB = 8, AC = 7, BD = 2 and CD = 1, find AD . SOLUTION: By applying the cosine law to 4 ABD and 4 ACD with respect to the angles ∠ ADB and ∠ ADC respectively, and canceling (since cos ∠ ADB = cos ∠ ADC ), we get AD = √ 2 13. √ ANSWER: 2 13 5 4