A high school space vector math problem, how to do this high school math space vector problem

Let the ad x-axis be d, the bc x-axis be c, and d be de bc, and de=bc

Then AD=3, BC=2, DC=5, ADE is a dihedral angle, so ADE=120°, in the triangle ADE, using the cosine theorem, AE= (3 2+2 2-2*3*2*cos120)= 19

be ae, so in the triangle AEB ab = (ae squared + be squared) = (19 + 25) = 2 11

<> "The solution is as above, and the minimum value of the vector modulus is 2 6

Semester 2 Senior 2 Mathematics Unit Questions (Exam time: 120 minutes Full score: 150 points) 1. Multiple choice questions (12 questions in total, 5 points each, 60 points in total) 1Known direction.

Senior 2 Mathematics Unit Questions (Exam time: 120 minutes Full score: 150 points) 1. Multiple choice questions (12 questions in total, 5 points each, 60 points in total) 1Known direction.

Now let the point n=(x,y,z) on the straight line l.

That is, the vector pn=(x-1,y,z+1).

Since l is parallel to the vector a

n=(5,2,1).

Vector pn=(4,2,2).

Vector pm=(0,2,4).

Vector mn = (4,0,-2).

Then bring in the four options.

But the answers I figured out were b and d, alas.

It's strange that you copied the wrong question......b：（1/4,-1,1/2）……At least that's what I wrote on my math homework paper......）

lz first draw a picture by myself, (6) I draw a1b1c1d1 on it, abcd on the bottom! Establish a spatial Cartesian coordinate system, with A as the origin, AB as the X-axis, and AD as the Y-axis.

6) Because the angle BAD=90°, ABCD and A1B1C1D1 are rectangular.

Whereas, with sporadic beats and angle baa1 = angle daa1 = 60°

From A1 to ABCD perpendicular line A1E, the perpendicular line from E to the AB side is EF, and the stupid perpendicular line from E to AD side is FG

According to the known conditions, ae = (3 root number, 2) 2, ac = root number, 5 according to the above conditions.

Determine the vector ac=(1,2,0), vector aa1 = vector cc1 = (,, root number 2) then vector ac1 = vector ac + vector cc1 = (,, root number 2) so ac1 = root number 23

18) This question is similar to the previous question, except that the angle DAB=60° leads from A1 to ABCD perpendicular line A1E, AE=root number 3, AC=2 root number 2 is obtained according to the above conditions.

Vector ac=(2, root number 3,0), vector aa1 = vector cc1 = (, root number 3, root number 6).

Then vector ac1 = vector ac+ vector cc1 = (, root number 3, root number 6) so ac1 = root number 25 = 5

I didn't think it through before, so I did it wrong!

The above process is a little brief, if you don't know how to dig losses, you can continue to ask me.

The score is too small, and no one wants to do it for you. Understand?

The values of x and y have been calculated.

It's to verify that the cd option is incorrect.