Posted by Jitesh on Wednesday, December 19, 2012 at 1:50pm.
The points A,B,C,D have coordinates (3,3), (8,0), (-1,1), (-6,4) respectively.
a) Find the gradients of the lines AB and CD
b) Show that ABCD is a parallelogram
c) Find the coordinates of the point of intersection of the diagnols AC and BD.
Please help me by showing all methods of working out answer.
Coordinate Geometry - Damon, Wednesday, December 19, 2012 at 2:07pm
I assume that by gradient you mean slope, m
m AB = (0-3)/(8-3) = -3/5
m CD = (4-1)/(-6+1) = -35
so AB and CD are parallel (same slope)
if DA and CB are also parallel, it is a parallelogram
m DA = (4-3)/(-6-3) = -1/9
m CB = (0-1)/(8+1) = -1/9
sure enough, parallelogram
where is the middle?
halfway between A and C (or D and B)
do A and C
average x = (-1 + 3)/2 = 1
average y = (1+3)/2 = 2
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