Why is the direction vector of a straight line parallel to the xoy plane (x, y, 0) in Higher Mathematics

If the line is parallel to the plane, the direction vector of the line is perpendicular to the normal vector of the plane. If the normal vector of the xoy plane is (0,0,1), and the direction vector of the line is perpendicular to it, then the Z coordinate of the direction vector is 0, so the direction vector is (x, y, 0)

Given that a direction vector of line L is a = (- 2,3,1) and a normal vector of plane B is u = (- 4,6,2), what is the relationship between L and B
In addition, if there are too many parallel vectors in space, how to calculate them with coordinates

Because u = 2A, so a / / u, so the line is perpendicular to the plane

When AC voltage is applied to the capacitor, does current flow through the circuit
Does the direction of the current change? Does the current pass through the insulating medium?

There is an electric current passing through
The direction of the current varies as the frequency of the alternating current
The current flows through the insulating medium

In inductive load circuit, why not use series capacitor to change the phase difference between current and voltage

Series capacitor. If there is partial voltage on the capacitor, then the voltage on the load and capacitor is not its rated value, so it is generally not used. If we simply change the phase between voltage and current, of course it is OK

2 / 9 * 3 / 8 + 0.375 + 7 / 9 * 37.5% simple operation

（2/9+1+7/9）*3/8=2*3/8=3/4
（0.375=3/8）

Given that the range of function FX = LG (AX ^ 2 + 2x + 11) is r, then the range of a is? If the range is [1, + infinite], then the range of a is

Let g (x) = ax ^ 2 + 2x + 11
The range of F (x) is r, which means that the range of G (x) contains all positive values
When a > 0, the minimum value should not be greater than 0, that is: delta = 4-44a > = 0, a is obtained

A rectangle is 10 cm long and 6 cm wide. If you cut out a square with 1 cm side length from its four corners, the perimeter of the remaining figure ()
A. Increase 4cm B. decrease 4cm C. same as before

As shown in the figure above, if a square with a side length of 1cm is cut out from each corner of the rectangle, the perimeter of the remaining figure will remain unchanged, just like the original

Please calculate the numbers given in the following questions by +, -, ×, △ and the result is 24 23 7 11 9 7 54 10 8 7 4
2 3 7 11 group 9 7 54 group 10 8 7 4 group

(11-7)×3 ×2 =24
8÷4× 7+10=24

Let the sum of the first n terms of the sequence {an} be Sn, and Sn = (λ + 1) - λ an, where λ is a constant not equal to - 1 and 0
Let the sum of the first n terms of the sequence {an} be Sn, and Sn = (λ + 1) - λ an, where λ is a constant not equal to - 1 and 0. (I) prove that an is an equal ratio sequence; (II) let the common ratio of the sequence {an} q = f (λ), and the sequence {BN} satisfy & nbsp;, BN = f (bn-1) (n ∈ n, n ≥ 2), and find the sum of the first n terms of the sequence (1 divided by BN) as TN

A piece of iron wire can just form a square with a side length of 6.28 cm. If the iron wire is used to form a circle, what is the area of the circle

Wire length = 6.28 × 4 = 25.12 (CM)
Radius of circle = 25.12 △ 3.14 △ 2 = 4 (CM)
Area of circle = 3.14 × 4 & # 178; = 50.24 (square centimeter)

Why is the direction vector of a straight line parallel to the xoy plane (x, y, 0) in Higher Mathematics