Question

Hello! Here is my question:
I have in space a line AB where A (0,0,0) and
B (3,5,10). I have a point C (4,7,9). I need to find on line AB a point D where the line CD intersects AB if this lines are perpendicular to each other. Please show step by step. Thanks.

Answer 1

Find vector AB.

Answer 2

ab = <3,5,10> right?

Answer 3

you need to determine if the lines even intersect

Answer 4

Very good. Now call D, xyz and find CD

Answer 5

<3,5,10>
<x, y, z>
---------
3x +5y +10z = 0

Answer 6

3(x-4t) +5(y-7t) +10(z-9t) = 0 right?

Answer 7

chaguanas can u help me with a math question

Answer 8

x = 3t
y = 5t
z = 10t is the equation of one line in space

Answer 9

amistre can u help me

Answer 10

x = x0+4t
y = y0+7t
z = z0+9t is the other.... i think

Answer 11

i can look at it, not sure if i can helptho :)

Answer 12

I do not remember how to find th Perpendicular

Answer 13

To find perpendicular is to find the normal, cross two vectors.

Answer 14

Vector U*V=0 right?

Answer 15

Yes, Amistre, found AB and CD. Actually, you just test them to see if they are perpendicular.

Answer 16

AB*CD=0

Answer 17

AB*CD=0

Answer 18

Yes, if you dot them and get 0, they are perpendicular

Answer 19

I will try. How do I find the normal, cross two vectors?

Answer 20

Yes that is how you found the normal. But in this case by the way the question was asked you were led to the answer to your question without having to do that.

Answer 21

Thanks