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Core 1 help please!

Question: I have found out 3 co-ordinates of a triangle (0,0), (0,-7) and (3,-6) from previous questions, now I am asked to find the area of this triangle. How is this possible if I don't know the height and all the lengths are different?

Thanks in advance!

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Reply 1

TenOfThem

Original post by luke5675

You do know both the base and the height

I suggest that you sketch a diagram and all should become clear

Reply 2

luke5675

Yes, sketch looks like right angled, but line (0,0) to (0,-7) is not perpendicular to the line (0-7) to (3,-6)? So this means that the height is not -7 as it is not a right angled triangle?

Reply 3

TenOfThem

Original post by luke5675

Yes, sketch looks like right angled, but line (0,0) to (0,-7) is not perpendicular to the line (0-7) to (3,-6)? So this means that the height is not -7 as it is not a right angled triangle?

It is not right angled but you have a base that is on one of the axes and therefore know the height

Reply 4

luke5675

Sorry about this, still slightly confused as would that not be the slanted height of triangle?

Reply 5

TenOfThem

Original post by luke5675

Sorry about this, still slightly confused as would that not be the slanted height of triangle?

I am not sure what you are looking at

Having drawn the triangle you should have a base (on the y-axis) and 2 slanting sides

Draw the height in - you should be able to see instantly how tall the triangle is

Reply 6

THEMathlete

Use pythagoras to find the distance between the points :smile:

Posted from TSR Mobile

Reply 7

TenOfThem

Original post by THEMathlete

Use pythagoras to find the distance between the points :smile:

Posted from TSR Mobile

Why

That will not help to solve this problem at all

Reply 8

luke5675

Sorry it took quite a while to see this, understand what you are saying now though. Thanks for your help! :smile:

Reply 9

TenOfThem

Original post by luke5675

Sorry it took quite a while to see this, understand what you are saying now though. Thanks for your help! :smile:

In C1 - all questions of this sort will have 2 co-ordinates that form the base then you you just need to draw in the height

Reply 10

techno-thriller

Find the lengths between the points

I.E distance= (x1-x2)^2+(y1-y2)^2 do for all sides the put each number on their respective side and use 1\2height x base

(edited 10 years ago)

Reply 11

TenOfThem

Original post by techno-thriller

Find the lengths between the points

I.E distance= (x1-x2)^2+(y1-y2)^2 do for all sides the put each number on their respective side and use 1\2heightxbase

This is nonsense - in no way does it help to solve the problem given

Reply 12

techno-thriller

Original post by TenOfThem

This is nonsense - in no way does it help to solve the problem given

I was just doing a problem like this.

Reply 13

Jatom

Triangle doesn't have to be right-angled :smile:

If the co-ordinates you gave are correct, then the area is 10.5 squared units

(edited 10 years ago)

photo.jpg481.4KB

Reply 14

Jatom

don't know why it's upside down! haha

Reply 15

TerribleTej

the base is seven and height is 3, and that can be derived from the question itself once you draw out the triangle on a graph. then your answer will be 0.5*base*height

Reply 16

TenOfThem

Original post by techno-thriller

I was just doing a problem like this.

incorrectly, I assume

there is no need for Pythagoras in this question

Reply 17

luke5675

Didn't expect so many responses to my first post! Thanks a lot for all of your feedback :smile:

Reply 18

TenOfThem

Original post by luke5675

Didn't expect so many responses to my first post! Thanks a lot for all of your feedback :smile:

Welcome to maths :biggrin:

Reply 19

BWV1007

Honestly... I think you can just use the formula

Area of triangle =
| x1 x2 x3 x1 |
| y1 y2 y3 y1 |

= 1/2[(x1 x y2) + (x2 x y3) + (x3 x y1) - (y1 x x2) - (y2 x x3) - (y3 x x1)]