1. in triangle ABC, if sinA=cosB-cosC, prove that triangle ABC is a right-angled triangle.
2. if A+B+C= 180degree and sinA=(sinB+sinC), prove that cot(B/2)cot(C/2)=3
3.GIVEN THAT cos3a+cos3b+cos3c=1-4sin((3a)/2)sin((3c)/2)sin((3b)/2)
in triangle xyz, prove that one of the angles of the triangle is 120degree if cos3x+cos3y+cos3z=1
m2 trigonometric functions
2011-03-17 3:20 am
回答 (3)
2011-03-17 8:10 am
✔ 最佳答案
Question 1:圖片參考：http://i707.photobucket.com/albums/ww74/stevieg90/ScreenHunter_02Mar162358.gif
Question 2:
圖片參考：http://i707.photobucket.com/albums/ww74/stevieg90/ScreenHunter_03Mar170003.gif
Question 3:
圖片參考：http://i707.photobucket.com/albums/ww74/stevieg90/ScreenHunter_04Mar170007.gif
2011-03-17 00:11:24 補充：
http://i707.photobucket.com/albums/ww74/stevieg90/ScreenHunter_02Mar162358.gif
http://i707.photobucket.com/albums/ww74/stevieg90/ScreenHunter_03Mar170003.gif
http://i707.photobucket.com/albums/ww74/stevieg90/ScreenHunter_04Mar170007.gif
2011-03-17 13:06:10 補充：
should be sinA=(sinB+sinC)/2
2011-03-18 5:39 am
yes, sorry, i typed it wrongly
2011-03-17 8:02 pm
2)
sinA=(sinB+sinC),
or
sinA=(sinB+sinC)/2,
sinA=(sinB+sinC),
or
sinA=(sinB+sinC)/2,
收錄日期: 2021-04-22 00:54:04
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20110316000051KK00905