Area of Triangle (Fast method, but is it allowed) (1 Viewer)

[_ShiFTy_]

At school, we learnt that to find the area of a triangle with coordinates (x1,y1),(x2,y2),(x3,y3) is

1 | (x1y2 + x2y3 + x3y1) - (x1y3 + x3y2 + x2y1) |
2 | |

Apparently its some method used in uni, but is it allowed in the HSC? My teacher says its ok but i wanna make sure..

 

[buchanan]

It used to be in the old Level 1 course:
http://community.boredofstudies.org/2220688-post2.html

It was taken out of the syllabus in 1980.

But it's still valid. So I'd say still use it. But Ian Woodhouse would say don't because it's not in the current syllabus, as he said last Saturday at the HSC feedback day in relation to another question:
http://www4.tpgi.com.au/nanahcub/2005hscfeedback.pdf

 

[buchanan]

I assure you it has been seen since 1980 and it should resonate with people today because it's all over the internet: eg., http://mathworld.wolfram.com/TriangleArea.html

 

[Mountain.Dew]

it seems fine to me, but i rarely see any questions that would involve that.

i suppose its a nice 'general' way of finding any area of a triangle, but for the HSC, there are hardly ANY questions were this would a superior or recommended method.

but, 06ers, its ur HSC. use it at ur own risk.

 

[buchanan]

use it at ur own risk.

Dare I say use it at Ian Woodhouse's risk.

It IS a superior method and therefore I do recommend using it, despite Ian Woodhouse (or perhaps more poignantly - BECAUSE of Ian Woodhouse........)

 

[Riviet]

I guess you could use it to quickly check your answer, instead of using it alone in your working.

 

[_ShiFTy_]

it seems fine to me, but i rarely see any questions that would involve that.

I've seen it a couple of times in Conics...usually its to prove that the area is a constant or something

 

[ur_inner_child]

why the damn hell would it be taken out in the 80s if it was always a valid method?

 

[Templar]

Just because it isn't in the syllabus doesn't mean that it isn't mathematically valid.

 

[ur_inner_child]

Just because it isn't in the syllabus doesn't mean that it isn't mathematically valid.

missed the point there didnt you

why was it taken OUT

 

[buchanan]

It was taken out (along with many other things) because the course was changed from a 2-year course to a 1-year course:
http://community.boredofstudies.org/2220688-post2.html

 

[Templar]

You missed my point too. It's a mathematically valid method regardless whether it's in the syllabus, got taken out of the syllabus, or was never in the syllabus.

The way you worded your question, it sounds like you're disputing its validity as a mathematical equation, simply because it was taken out of the syllabus.

 

[buchanan]

It got taken out because determinants and matrices got taken out. So when they went, so did this little area formula. It had nothing to do with validity.

 

[ur_inner_child]

You missed my point too. It's a mathematically valid method regardless whether it's in the syllabus, got taken out of the syllabus, or was never in the syllabus.

The way you worded your question, it sounds like you're disputing its validity as a mathematical equation, simply because it was taken out of the syllabus.

its a question from someone who didnt know what was going on. I don't question its validity, quite frankly I didnt even give it a second look. it was a honest question, answered pretty vaguely the first time.

It got taken out because determinants and matrices got taken out. So when they went, so did this little area formula. It had nothing to do with validity.

that answer is severely better.

Well apologies for the misunderstanding :/