Diagonal facts for kids
A diagonal line is a straight line that connects two corners of a shape. It does not go straight up, down, or across. Think of drawing a line from one corner of a square to the opposite corner. That's a diagonal!
In mathematics, the word "diagonal" is used in a few ways. Most often, it refers to lines inside shapes.
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What is a Diagonal Line?
A diagonal line connects two points that are not next to each other. For example, on a computer monitor, the size is often measured diagonally. This means measuring from one corner to the opposite corner.
Diagonals in Shapes
In geometry, a diagonal is a line segment that joins two non-adjacent vertices (corners) of a polygon.
- A square has four corners. If you draw lines between opposite corners, you will find two diagonals.
- A five-sided shape has five corners. It has five diagonals.
- A triangle has three sides and three corners. It does not have any diagonals because all its corners are next to each other.
Counting Diagonals in Polygons
You can figure out how many diagonals a polygon has using a simple formula. If a shape has 'n' sides (and 'n' corners), the number of diagonals can be found with this formula:
(n × (n - 3)) / 2
For example:
- For a square (n=4): (4 × (4 - 3)) / 2 = (4 × 1) / 2 = 4 / 2 = 2 diagonals.
- For a pentagon (n=5): (5 × (5 - 3)) / 2 = (5 × 2) / 2 = 10 / 2 = 5 diagonals.
This formula helps mathematicians quickly count diagonals in any polygon, no matter how many sides it has!
Images for kids
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A stand of basic scaffolding on a house construction site, with diagonal braces to maintain its structure
See also
In Spanish: Diagonal para niños
