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Help with C1 - Coordinate Geometry

I've posted this on the A level forum but I think I will get more help/response here..

Aha, I've been revising for a while.. but I just came across a question..

In coordinate geometry, i've been given 4 coordinates. Asked to draw it and show, by calculation, that it is a trapezium. Similar questions say show, by calculation, that it is a parallelogram etc.

Coordinates
A=0,0
B=0,3
C=6,6
D=12,6


Anyone know how I can do this? Thanks for the help! :smile:
Reply 1
draw it out
then apply the trapezuim formula 0.5h(a+b)
Ok, a trapesium has one pair of parallel lines and one pair that are not. In parallel lines you have the same gradient.

So if you draw sketch using the co-ordinates (or you can tell this from looking at the question) you will get the idea that BC should be parallel to AD, and BA should NOT be parallel to CD.

Gradient = Y2-Y1/X2-X1
BC= 3-6/0-6 = -3/-6 = 1/2
AD= 0-6/0-12 = -6/-12 = 1/2
Here we have proved that BC and AD are parallel as that are both y=1/2x + c

BA= 3-0/0-0 = 3
CD= 6-6/6-12 = -6/-6 = 1
Here we have proved that BA and CD are not parallel which is what I was expecting.

So, as far as I know that is the question answered.
If the shape was a parrallelogram, you would expect to find both the sets of opposite lines to have the same gradient.

Hope I helped :biggrin:
Reply 3
emilylikeeee
Ok, a trapesium has one pair of parallel lines and one pair that are not. In parallel lines you have the same gradient.

So if you draw sketch using the co-ordinates (or you can tell this from looking at the question) you will get the idea that BC should be parallel to AD, and BA should NOT be parallel to CD.

Gradient = Y2-Y1/X2-X1
BC= 3-6/0-6 = -3/-6 = 1/2
AD= 0-6/0-12 = -6/-12 = 1/2
Here we have proved that BC and AD are parallel as that are both y=1/2x + c

BA= 3-0/0-0 = 3
CD= 6-6/6-12 = -6/-6 = 1
Here we have proved that BA and CD are not parallel which is what I was expecting.

So, as far as I know that is the question answered.
If the shape was a parrallelogram, you would expect to find both the sets of opposite lines to have the same gradient.

Hope I helped :biggrin:


That really helped! Thank you SO much :smile:
pluuum
That really helped! Thank you SO much :smile:


Not a problem! It helps me to help other people any way. Good luck with your exams in June :smile:
Reply 5
whizz-kid
draw it out
then apply the trapezuim formula 0.5h(a+b)


Would that suffice for C1?

To the OP

Try using the distance formula/midpoint formula also purely to build skills and develop a conceptual understanding of whats going on when graphing linear functions

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