C4 Vectors

page 14 question 4 part C, 'find the distance of the point B from the line l1'

in the mark scheme it assumes that the angle AB makes with l1 is 90 degrees i think, but don't see why. Could someone please explain?

The Q4 (c) on page 14 asks you to show that two vectors are perpendicular.

There are no lines involved.

sorry i meant page 12

I can't see how the MS assumes that AB is perpendicular to l1.

They have just used the area of the triangle (half the area of the parallelogram) to find the distance.

Drawing a sketch might help you to understand what's going on

bump


could someone help me with question 7c, page 13? im still not getting it ;(

Having worked out the distance PQ, we know this to be the same as QR.

QR lies entirely on l2, and will be a scalar multiple of that line's direction vector.

By working out the length of the direction vector we can determine what the scalar multiple is; in this case 2.

OR = OQ +/- 2"direction vector of l2"

page 12 question 4 part C, 'find the distance of the point B from the line l1'

in the mark scheme it assumes that the angle AB makes with l1 is 90 degrees i think, but don't see why. Could someone please explain?

page 12 question 4 part C, 'find the distance of the point B from the line l1'

in the mark scheme it assumes that the angle AB makes with l1 is 90 degrees i think, but don't see why. Could someone please explain?