Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °

You are not logged in.

• Index
•  » Formulas
•  » geometry coordinates points on perimeter and points within shape

#1 2013-05-09 02:25:56

zxcvbnm123
Member

Offline

geometry coordinates points on perimeter and points within shape

i need to know the formula to get the coordinates that are on the perimeter and within the shape of square and rectangle. does anyone know that?

lets say square coordinates of (1,1) , (1,3) , (3,3) , (3,1)

points on perimeter would be (1,2) , (2,1) , (2,3) , (3,2) excluding the actual coordinates above.

points within shape would be (2,2)

#2 2013-05-09 02:27:53

bob bundy
Moderator

Offline

Re: geometry coordinates points on perimeter and points within shape

hi zxcvbnm123

Welcome to the forum.

I seem to remember there is a formula, so I'll try to find it.  Failing that, maybe I can work it out.

Back soon.

EDIT:  This is the one I remembered:

http://en.wikipedia.org/wiki/Pick's_theorem

It's not quite what you want, but it'll give you a start.

Are the sides of the shapes parallel to the axes ?  (Harder if not)

Bob

You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

#3 2013-05-09 02:46:47

zxcvbnm123
Member

Offline

Re: geometry coordinates points on perimeter and points within shape

yes all lines and sides are parallel

#4 2013-05-09 03:53:26

anonimnystefy
Real Member

Offline

Re: geometry coordinates points on perimeter and points within shape

Do you want just points with integer coordinates?

The limit operator is just an excuse for doing something you know you can't.
“It's the subject that nobody knows anything about that we can all talk about!” ― Richard Feynman
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment

#5 2013-05-09 04:21:31

zxcvbnm123
Member

Offline

Re: geometry coordinates points on perimeter and points within shape

yes just need point with integer . the type of answer i need is what i shown above.

#6 2013-05-09 04:27:23

anonimnystefy
Real Member

Offline

Re: geometry coordinates points on perimeter and points within shape

Well, for the points on the edges, if the square's coordinates are (a,a), (a,b), (b,a) and (b,b), they are:

(a,a+k), 0<k<b-a
(b,a+k), 0<k<b-a
(a+k,a), 0<k<b-a
(a+k,b), 0<k<b-a

As for the points inside the square, they all have coordinates of the form:

(a+k,a+l), 0<k,l<b-a

Last edited by anonimnystefy (2013-05-09 04:28:03)

The limit operator is just an excuse for doing something you know you can't.
“It's the subject that nobody knows anything about that we can all talk about!” ― Richard Feynman
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment

#7 2013-05-09 06:18:47

zxcvbnm123
Member

Offline

Re: geometry coordinates points on perimeter and points within shape

i am sorry, i am very new to geometry coordinates... i dont understand your formula...can give me one example how you use that formula to get the answers?

#8 2013-05-09 06:26:08

anonimnystefy
Real Member

Offline

Re: geometry coordinates points on perimeter and points within shape

Hm, well, let's try with a=1 and b=4.

That would be the square (1,1), (1,4), (4,1), (4,4).

If draw it in the Cartesian coordinate system, you will see that the point on the edge are (1,2), (1,3), (2,1), (2,4), (3,1), (3,4), (4,2) and (4,3). By the formulas above we get:

(1,1+k), for 0<k<3, which gives (1,1+1)=(1,2) and (1,1+2)=(1,3)
(4,1+k), for 0<k<3, which gives (4,1+1)=(4,2) and (4,1+2)=(4,3)
(1+k,1), for 0<k<3, which gives (1+1,1)=(2,1) and (1+2,1)=(3,1)
(1+k,4), for 0<k<2, which gives (1+1,4)=(2,4) and (1+2,4)=(3,4)

If you compare the two sets of points, you will see we got the same points by drawing the square on the grid and by the formulas above.

Oh, just wondering, what do you need this for?

Last edited by anonimnystefy (2013-05-09 06:26:32)

The limit operator is just an excuse for doing something you know you can't.
“It's the subject that nobody knows anything about that we can all talk about!” ― Richard Feynman
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment

#9 2013-05-09 07:11:38

zxcvbnm123
Member

Offline

Re: geometry coordinates points on perimeter and points within shape

some homework unrelated to maths...and we need to create this formula

#10 2013-05-09 07:16:36

anonimnystefy
Real Member

Offline

Re: geometry coordinates points on perimeter and points within shape

Programming, maybe?

Are you a bit clearer about the formulas?

The limit operator is just an excuse for doing something you know you can't.
“It's the subject that nobody knows anything about that we can all talk about!” ― Richard Feynman
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment

#11 2013-05-09 11:08:06

zxcvbnm123
Member

Offline

Re: geometry coordinates points on perimeter and points within shape

yes thank you very much , brilliant formula . rushing my work now

#12 2013-05-09 11:35:06

zxcvbnm123
Member

Offline

Re: geometry coordinates points on perimeter and points within shape

can give me a example on how you get the answer for points within shape?  and i think l is l<b not l<b-a

#13 2013-05-09 18:21:37

anonimnystefy
Real Member

Offline

Re: geometry coordinates points on perimeter and points within shape

Well, if we take the square as in the last example, we know that the points inside the square are (2,2), (2,3), (3,2) and (3,3).

What do you get when you do
(1+k,1+l), for 0<k<3, 0<l<3?

The limit operator is just an excuse for doing something you know you can't.
“It's the subject that nobody knows anything about that we can all talk about!” ― Richard Feynman
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment

#14 2013-05-09 22:03:28

zxcvbnm123
Member

Offline

Re: geometry coordinates points on perimeter and points within shape

its ok i got it already

#15 2013-05-10 04:19:20

anonimnystefy
Real Member

Offline

Re: geometry coordinates points on perimeter and points within shape

That is great!

The limit operator is just an excuse for doing something you know you can't.
“It's the subject that nobody knows anything about that we can all talk about!” ― Richard Feynman
“Taking a new step, uttering a new word, is what people fear most.” ― Fyodor Dostoyevsky, Crime and Punishment

• Index
•  » Formulas
•  » geometry coordinates points on perimeter and points within shape