因为|A|=2,|B|=3所以设x1=2coaa,Y1=2sina,X2=3cosb,Y2=3sinb
因为A*B=6cosacosb+6sinasinb=6cos(a-b)=-6
所以cos(a-b)=-1.所以a-b=2kπ+π
所以
(X1+Y1)/(X2+Y2)
=2(cosa+sina)/[3(cosb+sinb)]
=2/3 *[sin(a+π/4)/sin(b+π/4)]
=2/3 *[sin(b+2kπ+π+π/4)/sin(b+π/4)]
=2/3 *[-sin(b+π/4)/sin(b+π/4)]
=-2/3.
已知向量A(X1,Y1),B(X2,Y2),|A|=2,|B|=3,A*B=-6,求(X1+Y1)/(X2+Y2)=?
已知向量A(X1,Y1),B(X2,Y2),|A|=2,|B|=3,A*B=-6,求(X1+Y1)/(X2+Y2)=?
数学人气:758 ℃时间:2020-05-02 05:29:16
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