2016韓國代購網 , 韓國代購化妝品 , 韓國代購批發 , 韓國代購教學---韓國代購/追加/寄貨

(1)0×9=0

(2)√81=9

(3)cot(45º)=tan(45º)=1

(4)log 2=0.3010; log 3=0.4771; 1<=a<10

2^30=a×10^k => 2^30/a=10^k

log(10)^k=log(2*^30/a)

k=30*log(2)-log(a)

=30*0.3010-log(1~10)

=9.03-(0~1)

=9.03~8.03

(5)某次模擬考,自然組數學一科,第二類組學生Nx=200人,平均成績Xbar=71分.標

準差為Sx=4分,第三類組學生N2=100人,平均成績Ybar=77分,標準差為Sy=5分,兩

類組學生300人之標準差為(四捨五入)?

Xbar=ΣX/200 => ΣX=200*Xbar=200*71=14200

Ybar=ΣY/100 => ΣY=100*Ybar=100*77=7700

Wbar=Σ(X+Y)/300=(14200+7700)/300=73

Vx=ΣX^2/200-Xbar^2=16

=> ΣX^2=200(Vx+Xbar^2)=200*(16+71^2)=1,011,400

Vy=ΣY^2/100-Ybar^2=25

=> ΣY^2=100(Vy+Ybar^2)=100*(25+77^2)=595,400

V=Σ(X^2+Y^2)/300-Wbar^2

=(1011400+595400)/300-73^2

=5356-5329

=27

S=√27=3√3=5.196........ans

This entry passed through the Full-Text RSS service — if this is your content and you're reading it on someone else's site, please read the FAQ at fivefilters.org/content-only/faq.php#publishers. Five Filters recommends: 'You Say What You Like, Because They Like What You Say' - http://www.medialens.org/index.php/alerts/alert-archive/alerts-2013/731-you-say-what-you-like-because-they-like-what-you-say.html