Maths c4 vectors

Hi was wondering if anyone could help me with part 3, was thinking it was the dot cross product but I don't know what to compare it to

Reply 1

TenOfThem

18

Original post by singapaul

Hi was wondering if anyone could help me with part 3, was thinking it was the dot cross product but I don't know what to compare it to

Is there a question
What do you mean by dot cross
What board do you do

Reply 2

singapaul

OP

8

Original post by TenOfThem

Is there a question
What do you mean by dot cross
What board do you do

Trying to attach the photo, basically a line with equation r= (2,3,5) +(lambda)(1,1,-0.5) meets a plane x+5y+2z=77
, I calculated the coordinates of b to be (12,13,0)
Then part 3 asks, find the angle which AB makes with the upward verticle, the answer is 109.5(degrees), but I don't know how to get to it

Reply 3

singapaul

OP

8

Original post by singapaul

Trying to attach the photo, basically a line with equation r= (2,3,5) +(lambda)(1,1,-0.5) meets a plane x+5y+2z=77
, I calculated the coordinates of b to be (12,13,0)
Then part 3 asks, find the angle which AB makes with the upward verticle, the answer is 109.5(degrees), but I don't know how to get to it

It's OCR mei

Reply 4

TenOfThem

18

Original post by singapaul

Trying to attach the photo, basically a line with equation r= (2,3,5) +(lambda)(1,1,-0.5) meets a plane x+5y+2z=77
, I calculated the coordinates of b to be (12,13,0)
Then part 3 asks, find the angle which AB makes with the upward verticle, the answer is 109.5(degrees), but I don't know how to get to it

Ok

We only do Planes in FM for edexcel so I would have to swot up

BUT, from vague memory

You can find the direction perpendicular to the plane can't you - so just dot that with (1,1, -0.5)

Reply 5

davros

16

Original post by singapaul

Trying to attach the photo, basically a line with equation r= (2,3,5) +(lambda)(1,1,-0.5) meets a plane x+5y+2z=77
, I calculated the coordinates of b to be (12,13,0)
Then part 3 asks, find the angle which AB makes with the upward verticle, the answer is 109.5(degrees), but I don't know how to get to it

If you want specific help, you're going to need to post the full question - you haven't even told us what point A is! And is the "upward vertical" the positive k-direction, i.e. unit vector (0,0,1)?

As TenOfThem says, you probably want to write the equation of the plane in vector form and use the dot product.

Reply 6

the bear

20

I am au fait* with the MEI syllabus.

you need to use the normal vector and the direction vector of the line.

calculate cosA using n.d/{|n|*|d|}

this gives the angle between the line and the normal.

if they also ask for the angle between the line and the plane you would subtract 90 degrees in this case.

LANGUAGE COMPLIANCE

*this means at the fact