Math Is Fun Forum

model

Member

Registered: 2011-08-10

Posts: 142

Area and perimeter of shapes

Hy all ,

I have two question about area and perimeter .

So first Area :

* Area is the number of pixels within a region.
* And Area can be find as quadtree . but how ?
Say  i have an image 10 * 10 . how  can we find area by representating an image in form of quadtree ?

* How can we find area using polygon vertices ?

Second about Perimeter :

Perimeter is the number pixels in the boundary  of  shape .

let  say i have an square of 4*4 . What's the perimeter of it  ?
and let say i have triangle
like
*
**
***   in the stared triangle, What is the perimeter ?
Please help me to understand ti .
I need to know about these  as soon as possible until tomorrow .
Expecting a good response thanks

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Maths is Doctor that make our life easy ..

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model

Member

Registered: 2011-08-10

Posts: 142

Re: Area and perimeter of shapes

Let say i have square like as shown in this link,.
http://www.mathsisfun.com/geometry/perimeter.html

In the square we have 4 sides . that meant perimeter is 3 + 7+ 3+ 7 = 15
My question is : what is the area of that square in the link .

In my understanding ,i think that square have 3 columns and 7 rows  which mean the area is 3*7  = 21 pixels is area of that square .

Am i right ?
Please help me to understand it .thanks

---

Maths is Doctor that make our life easy ..

https://www.facebook.com/groups/Maths.GIS/

Bob

Administrator

Registered: 2010-06-20

Posts: 10,803

Re: Area and perimeter of shapes

hi model

Let say i have square like as shown in this link,.
http://www.mathsisfun.com/geometry/perimeter.html

In the square we have 4 sides . that meant perimeter is 3 + 7+ 3+ 7 = 15
My question is : what is the area of that square in the link .

Correction perimeter = 3 + 7 + 3 + 7 = 20

It is just the distance around the outside.

And the area is just a measure of how many squares (see my picture) fit inside the shape.

In this case 3 rows with 7 squares in each row.

What I don't understand is why you want to use 'quadtrees' (had to look this up).

Are you in the middle of a computing task.  It might help us to help you if you gave the background to this question.
What do you know about a shape and why do you want the perimeter and area?

For example: Given the coordinates of all the points, there are formulas to give both perimeter and area.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob