How to find vector that is parallel to parametric vector? The line r = i + ( 1 + 3t )j - ( 3 - 4t )k passes through p_1=(1,1,−3) and is parallel to v = 3j + 4k. But why can we say that this is parallel?

Deromediqm

Deromediqm

Answered question

2022-07-14

I have a question on the following:
The line r = i + ( 1 + 3t )j - ( 3 - 4t )k passes through p 1 = ( 1 , 1 , 3 ) and is parallel to v = 3j + 4k.
But why can we say that this is parallel? And how can I apply this for different problems.
If someon could help me, it would be very much appreciated

Answer & Explanation

Anaya Gregory

Anaya Gregory

Beginner2022-07-15Added 14 answers

r = i ^ + j ^ 3 k ^ + t ( 3 j ^ + 4 k ^ ) , t R represents the equation of a straight line that passes through the point with position vector i ^ + j ^ 3 k ^ (take t=0). Take any two distinct points on the line, say for t 1 t 2 R
r 1 = i ^ + j ^ 3 k ^ + t 1 ( 3 j ^ + 4 k ^ ) r 2 = i ^ + j ^ 3 k ^ + t 2 ( 3 j ^ + 4 k ^ )
Then r 1 r 2 is a vector that is parallel to the line, i.e. the line is parallel to ( t 1 t 2 ) ( 3 j ^ + 4 k ^ ) or put simply, the line is parallel to 3 j ^ + 4 k ^
The information about a vector that is parallel to a line is as important as the information about the normal to a plane. It comes in handy in almost all applications involving lines, such as finding the distance of a point from the line, finding the image of a point with respect to a line, finding the angle between a line and a plane, etc..

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