OpenStudy (anonymous):

Find the distance the point P(-1,7,7) is to the line through the two points Q(-1,5,3), and R(-2,2,6)

2 years ago
OpenStudy (triciaal):

you may want to plot the points to "see" them better use the distance formula to find the length of the lines

2 years ago
OpenStudy (anonymous):

i plotted the points but its hard for me to visualize in 3d, even after plotting them

2 years ago
OpenStudy (triciaal):

@ganeshie8 will you please help, didn't realize this has 3 coordinates

2 years ago
OpenStudy (anonymous):

Oh I think I need to find midpoint between Q and R and then use distance formula to the midpoint!! maybe, trying now

2 years ago
OpenStudy (triciaal):

@billj5 same principle but not the best person for 3 coordinates, sorry

2 years ago
OpenStudy (anonymous):

@triciaal actually I don't think the midpoint matters :(

2 years ago
OpenStudy (triciaal):

@Hero pleasehelp

2 years ago
OpenStudy (anonymous):

@triciaal thank you :)

2 years ago
OpenStudy (anonymous):

still don't have it yet

2 years ago
OpenStudy (triciaal):

trying to get you some help from people whose work I trust

2 years ago
OpenStudy (anonymous):

I really appreciate that

2 years ago
OpenStudy (triciaal):

i think jim went off already

2 years ago
OpenStudy (anonymous):

ah no problem, thanks for the help, I will check back later or tomorrow

2 years ago
OpenStudy (anonymous):

I'm assuming this question means the shortest distance but not sure.

2 years ago
ganeshie8 (ganeshie8):

hey still stuck on this ?

2 years ago
OpenStudy (anonymous):

@ganeshie8 Thank you for the video, I'm still not getting it.

2 years ago
OpenStudy (rational):

still looking for help ?

2 years ago
OpenStudy (anonymous):

@rational yes

2 years ago
OpenStudy (rational):

familiar with cross product ?

2 years ago
OpenStudy (anonymous):

yes, I have done a few

2 years ago
OpenStudy (rational):

you must be knowing that the magnitude of cross product of two vectors gives the area of parallelogram made by those two vectors ?

2 years ago
OpenStudy (anonymous):

yes

2 years ago
OpenStudy (anonymous):

and 1/2 of that is the area of a triangle

2 years ago
OpenStudy (rational):

can we say |QR x QP| is the area of parallelogram formed by vectors QR and QP ?

2 years ago
OpenStudy (anonymous):

ah yes, I don't really understand why but I know that formula

2 years ago
OpenStudy (anonymous):

so I need height which is |a| sin $$\theta$$?

2 years ago
ganeshie8 (ganeshie8):

|dw:1421550410813:dw|

2 years ago