中四數學問題一個

JACKYPKPKPK789

k=sin30+cos60+sin90+...+sin1890+cos1920  ,問k=??

vin712

k=1.5先岩= =
琴晚計錯野打左2= =不好意思=3="

maxycy

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

vin712

k=sin30+cos60+sin90+...+sin1890+cos1920
=sin30+sin90+sin150+sin210+sin270+sin330+sin390+...+sin183 ...
maxycy 發表於 29-5-2011 21:48

    @+@ 琴日都用過呢個方法~但我唔肯定....之後我用cal 一個個咁嘟....就.....

vin712

vincent,你吾會真系用計數機逐個咁禁嫁可=.=?!
_銘記於心` 發表於 30-5-2011 01:29

    = =我用左3個方法計....最未有2個答案...所以今朝用cal一個個禁- -

maxycy

@+@ 琴日都用過呢個方法~但我唔肯定....之後我用cal 一個個咁嘟....就..... ...
vin712 發表於 30-5-2011 01:29

邊有唔肯定架=.=
全部都係FIXED VALUE
唔會出2個答案架啵

vin712

邊有唔肯定架=.=
全部都係FIXED VALUE
唔會出2個答案架啵
maxycy 發表於 30-5-2011 08:44

    我覺得好似計錯ma...之後嘟機嘟左1.5出黎= =
    你係咪打錯左+/-..cos1920=-0.5  A_A?...

maxycy

我覺得好似計錯ma...之後嘟機嘟左1.5出黎= =
    你係咪打錯左+/-..cos1920=-0.5  A_A?... ...
vin712 發表於 30-5-2011 10:01

係啵0.0
thx~