amaths
2007-11-24 4:12 am
Given that A(1,2),B(5,-1),C(4,k) are three points on x-y plane.If angleCAB=45degrees,find the two possible values of k
回答 (1)
2007-11-24 5:19 am
✔ 最佳答案
SET AC slope=mAB slope= -0.75
tan 45 = (m+0.75)/(1-0.75m) or -tan 45=(m+0.75)/(1-0.75m)
1-0.75m=m+0.75 or 0.75m-1=m+0.75
m= 1/7 or m= 7
(2-k)/(1-4) =1/7 or (2-k)/(1-4) =7
14-7k=-3 or 2-k=-21
k=11/7 or k=23
2007-11-23 21:22:02 補充：
k=17/7 or k=23sorry....最尾做錯咗
2007-11-23 21:25:40 補充：
no0.75m-1=m 0.75m=-7(2-k)/(1-4)=-7 or (2-k)/(1-4) =1/72-k=21 or 14-7k=-3 k=-19 or k=17/7
收錄日期: 2021-04-29 19:46:39
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https://hk.answers.yahoo.com/question/index?qid=20071123000051KK03267