2.3平面向量的数量积1.已知向量a、b满足|a|=3,|b|=2,|a+b|=4,则|a-b|=_____.2.已知|a|=|b|=1,a与b的夹角是90度,c=2a+3b,d=Ka-4b,c与d垂直,则K的值为_____.3.已知|a|=|b|=|a-b|=1,那么|a+b|=_______.
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![2.3平面向量的数量积1.已知向量a、b满足|a|=3,|b|=2,|a+b|=4,则|a-b|=_____.2.已知|a|=|b|=1,a与b的夹角是90度,c=2a+3b,d=Ka-4b,c与d垂直,则K的值为_____.3.已知|a|=|b|=|a-b|=1,那么|a+b|=_______.](/uploads/image/z/1076647-31-7.jpg?t=2.3%E5%B9%B3%E9%9D%A2%E5%90%91%E9%87%8F%E7%9A%84%E6%95%B0%E9%87%8F%E7%A7%AF1.%E5%B7%B2%E7%9F%A5%E5%90%91%E9%87%8Fa%E3%80%81b%E6%BB%A1%E8%B6%B3%7Ca%7C%3D3%2C%7Cb%7C%3D2%2C%7Ca%2Bb%7C%3D4%2C%E5%88%99%7Ca-b%7C%3D_____.2.%E5%B7%B2%E7%9F%A5%7Ca%7C%3D%7Cb%7C%3D1%2Ca%E4%B8%8Eb%E7%9A%84%E5%A4%B9%E8%A7%92%E6%98%AF90%E5%BA%A6%2Cc%3D2a%2B3b%2Cd%3DKa-4b%2Cc%E4%B8%8Ed%E5%9E%82%E7%9B%B4%2C%E5%88%99K%E7%9A%84%E5%80%BC%E4%B8%BA_____.3.%E5%B7%B2%E7%9F%A5%7Ca%7C%3D%7Cb%7C%3D%7Ca-b%7C%3D1%2C%E9%82%A3%E4%B9%88%7Ca%2Bb%7C%3D_______.)
2.3平面向量的数量积1.已知向量a、b满足|a|=3,|b|=2,|a+b|=4,则|a-b|=_____.2.已知|a|=|b|=1,a与b的夹角是90度,c=2a+3b,d=Ka-4b,c与d垂直,则K的值为_____.3.已知|a|=|b|=|a-b|=1,那么|a+b|=_______.
2.3平面向量的数量积
1.已知向量a、b满足|a|=3,|b|=2,|a+b|=4,则|a-b|=_____.
2.已知|a|=|b|=1,a与b的夹角是90度,c=2a+3b,d=Ka-4b,c与d垂直,则K的值为_____.
3.已知|a|=|b|=|a-b|=1,那么|a+b|=_______.
2.3平面向量的数量积1.已知向量a、b满足|a|=3,|b|=2,|a+b|=4,则|a-b|=_____.2.已知|a|=|b|=1,a与b的夹角是90度,c=2a+3b,d=Ka-4b,c与d垂直,则K的值为_____.3.已知|a|=|b|=|a-b|=1,那么|a+b|=_______.
1.(|a+b|)^2=a^2+b^2+2*a*bcosC=9+4+2*abcosC=16
2abcosC=3
(|a-b|)^2=a^2+b^2+2*a*bcosC=9+4-2*abcosC=10
2.c .d=(2a+3b).(Ka-4b)=2Ka^2-8a.b+3Ka.b-12b^2
a.b=0
c.d=2Ka^2-12b^2=2K-12=0
K=6
3.|a-b|^2=a^2+b^2-2abcosC=1+1-2abcosC=1
2abcosC=1
|a+b|^2=a^2+b^2+2abcosC=3
|a+b|=根号3
第一题根号10,第二题6,第三题根号3.
不太会打字,谢谢