Prove the following identities:
1.sin3αsin3α+cos3αcos3α=cos32α
2.cosA-cos2A=6sin^2 (A/2)-8sin^4 (A/2)
3.4cosAcos(2π/3+A)+cos(2π/3-A)=cos3A
4.(cosB-cosA)/(cosB+cosA)=[tan(A+B)/2][tan(A-B)/2]
F.4 A.Maths Trigo Question1
2009-02-08 4:57 am
回答 (1)
2009-02-08 6:26 am
✔ 最佳答案
L.H.S.=cosA-cos2A圖片參考：http://g.imagehost.org/0531/ScreenHunter_06_Feb_07_22_35.gif
=R.H.S.
2009-02-07 23:08:34 補充：
4.
http://g.imagehost.org/0802/ScreenHunter_07_Feb_07_23_17.gif
2009-02-07 23:25:56 補充：
1.
http://g.imagehost.org/0834/ScreenHunter_08_Feb_07_23_36.gif
2009-02-13 23:04:10 補充：
2.
http://f.imagehost.org/0610/ScreenHunter_02_Feb_13_23_01.gif
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