单位向量a,b的夹角为2π/3
a*b=|a||b|cos2π/3=1*1*(-1/2)=-1/2
|2a-3b|^2=4a^2-12a*b+9b^2=4*1-12*(-1/2)+9*1=19
故|2a-3b|=根号19
已知单位向量a,b的夹角为2π/3,则向量2a-3b的模等于
已知单位向量a,b的夹角为2π/3,则向量2a-3b的模等于
数学人气:775 ℃时间:2020-03-22 10:37:33
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