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本帖最後由 maxycy 於 30-5-2011 13:44 編輯
k=1.5先岩= =
琴晚計錯野打左2= =不好意思=3="
vin712 發表於 29-5-2011 01:44
k=sin30+cos60+sin90+...+sin1890+cos1920
=sin30+sin90+sin150+sin210+sin270+sin330+sin390+...+sin1830+sin1890
+cos60+cos120+cos180+cos240+cos300+cos360+cos420+...+cos1860+cos1920
=(0.5+1+0.5-0.5-1-0.5)x(1800/360)+sin1830+sin1890+(0.5-0.5-1-0.5+0.5+1)x(1800/360)+cos1860+cos1920
=0x5+sin30+sin90+0x5+cos60+cos120
=0.5+1+0.5-0.5
=1.5 |
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