Show that Ө = β /3
( 2cos2Ө - 2cos(β - Ө))
更新1:
cos2Ө = cos(β - Ө) Why do you cancel the cos in both side?
更新2:
0< Ө < 90 < β < 180 ????
更新3:
If Ө = 70, β = 210 ??? Out of the range.
Urgent question
2009-01-04 8:15 pm
Show the steps in a detailed way.
Show that Ө = β /3
( 2cos2Ө - 2cos(β - Ө))
Show that Ө = β /3
( 2cos2Ө - 2cos(β - Ө))
回答 (1)
2009-01-04 8:25 pm
✔ 最佳答案
因為若dS/dӨ=0
r^2 ( cos2Ө - cos(β - Ө) )=0
cos2Ө - cos(β - Ө) =0
cos2Ө = cos(β - Ө)
2Ө = (β - Ө)
3Ө = β
Ө = β/3
2009-01-04 12:28:17 補充：
因為你看Ө 和 β的角度範圍知道可行
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原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20090104000051KK00629