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Known vector A =(3,2), B =(x,4) and A∥ B, the value of x is () A.-6 B.6 C.8 3 D.-8 3
Because
A =(3,2),
B =(x,4) and
A∥
B,
So 2x-3×4=0, the solution can get x=6
Reason selection B
Because
A =(3,2),
B =(x,4) and
A∥
B,
So 2x-3×4=0, the solution can get x=6
Therefore, select B
Given the plane vector a=(3,1), vector b=(x,-3), and vector a perpendicular to vector b, what is the value of x?
Vector a⊥ vector b,
So vector a·vector b=0
Therefore, x1x2+y1y2=0, i.e.3*1+x*(-3)=0
X =1
Given vector a=(2,-3), b=(-3,1).a*b=
Solution
A*b
=2×(-3)+(-3)×1
=-6-3
=-9
Given vector a=(4,2), b=(1,3) 1. Find the included angle X of a, b 2. If (vector a + unknown * vector b) is perpendicular to vector b, find the unknown
1. Ab=4+2*3=10
Cosa=10/(2√5 10)=√2/2
Therefore, the included angle is π/4, i.e.45°.
2. Subject meaning
(A+input b) b=ab+input b2=10+input*10=0
In =-1
If vector a=(-2,1), b=(1,-3), the angle between vector a and b is ________ The answer is 3/4π If vector a=(-2,1), b=(1,-3), the angle between vector a and b is ________ Answer 3/4π
Parse
| A |=√5
|B 10
Cos=ab/|a||b|
=(-2-3)/√50
=-5/√50
=-√2/2
Cos3π/4=-√2/2
A (3.2) b (1.1) Find the vector ab?
Subtract the coordinates of a from the coordinates of b (-2,-1)
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