x=a+b,y=2a+b ,且 |a| = |b| = 1 ,a⊥b (1) 求 |x|,|y|; (2) 若x与yx=a+b,y=2a+b ,且 |a| = |b| = 1 ,a⊥b(1) 求 |x|,|y|;(2) 若x与y的夹角为θ,求cosθ的值.
来源:学生作业帮助网 编辑:作业帮 时间:2024/07/06 19:31:27
![x=a+b,y=2a+b ,且 |a| = |b| = 1 ,a⊥b (1) 求 |x|,|y|; (2) 若x与yx=a+b,y=2a+b ,且 |a| = |b| = 1 ,a⊥b(1) 求 |x|,|y|;(2) 若x与y的夹角为θ,求cosθ的值.](/uploads/image/z/6962673-57-3.jpg?t=x%3Da%2Bb%2Cy%3D2a%2Bb+%2C%E4%B8%94+%7Ca%7C+%3D+%7Cb%7C+%3D+1+%2Ca%E2%8A%A5b+%281%29+%E6%B1%82+%7Cx%7C%2C%7Cy%7C%EF%BC%9B+%282%29+%E8%8B%A5x%E4%B8%8Eyx%3Da%2Bb%2Cy%3D2a%2Bb+%2C%E4%B8%94+%7Ca%7C+%3D+%7Cb%7C+%3D+1+%2Ca%E2%8A%A5b%281%29+%E6%B1%82+%7Cx%7C%2C%7Cy%7C%EF%BC%9B%282%29+%E8%8B%A5x%E4%B8%8Ey%E7%9A%84%E5%A4%B9%E8%A7%92%E4%B8%BA%CE%B8%2C%E6%B1%82cos%CE%B8%E7%9A%84%E5%80%BC.)
x=a+b,y=2a+b ,且 |a| = |b| = 1 ,a⊥b (1) 求 |x|,|y|; (2) 若x与yx=a+b,y=2a+b ,且 |a| = |b| = 1 ,a⊥b(1) 求 |x|,|y|;(2) 若x与y的夹角为θ,求cosθ的值.
x=a+b,y=2a+b ,且 |a| = |b| = 1 ,a⊥b (1) 求 |x|,|y|; (2) 若x与y
x=a+b,y=2a+b ,且 |a| = |b| = 1 ,a⊥b
(1) 求 |x|,|y|;
(2) 若x与y的夹角为θ,求cosθ的值.
x=a+b,y=2a+b ,且 |a| = |b| = 1 ,a⊥b (1) 求 |x|,|y|; (2) 若x与yx=a+b,y=2a+b ,且 |a| = |b| = 1 ,a⊥b(1) 求 |x|,|y|;(2) 若x与y的夹角为θ,求cosθ的值.
这不是很简单吗,画一下图就出来了.
|x|=(A^2+B^2)开根号=根号2
同理|y|=跟号5
x* y=(a+b)*(2a+b)=2a^2+b^2+3ab
=2+1=3=|x|*|y|*cosθ=cosθ*根号10
所以 cosθ=十分之三根号10
向量问题 x=a+b,y=2a+b , 且 |a| = |b| = 1 , a⊥b
(1) 求 |x|, |y|;
|x|^2=(a+b)*(a+b)=a*a+2ab+b*b=2
|y|* |y|=(2a+b)*(2a+b)=4a^2+4ab+b^2=5
|x|=根2
|y|=根5
(2) 若x与y的夹角为θ,求cosθ的值
|...
全部展开
向量问题 x=a+b,y=2a+b , 且 |a| = |b| = 1 , a⊥b
(1) 求 |x|, |y|;
|x|^2=(a+b)*(a+b)=a*a+2ab+b*b=2
|y|* |y|=(2a+b)*(2a+b)=4a^2+4ab+b^2=5
|x|=根2
|y|=根5
(2) 若x与y的夹角为θ,求cosθ的值
|x|^2=(a+b)*(a+b)=a*a+2ab+b*b=2+2 |a| |b| cosθ
|y|* |y|=(2a+b)*(2a+b)=4a^2+4ab+b^2=5+4|a| |b| cosθ
你第二问是不是缺少什么条件?
收起