At 9 a.m,a hiker was due south of point P. What direction was point P from her position at noon?
(1)From 9 a.m until 11 a.m she walked due east at 2 miles per hour, and from 11 a.m until noon, she walked due north at 3 miles per hours.
(2)At noon,she is exactly 4.5 miles from point P
答案选的是E,为什么不是C呢?
这个题目相当的tricky.
从起点往东走了4 miles,往北走了3公里.
如果这点距离P 正好4.5公里,那么其实只有两种可能.
假设p为原点,那么终点的这两种可能是:
(4, ((4.5)^2-4^2)^(1/2)) 和(4, -((4.5)^2-4^2)^(1/2))
当然画图非常方便.
但我觉得,如果这个半径不是4.5, 比如说5, 那么这个题目答案是C.
请大侠指正!
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