59 lines
2.4 KiB
Markdown
59 lines
2.4 KiB
Markdown
---
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title: 2d Shapes Polygons and More
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---
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## 2d Shapes Polygons and More
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'2D' stands for 2-dimensional. A 2D shape is any shape that has two dimensions. Think about what it means to have two dimensions for a moment. If we had only one dimension to work with, we could only move backwards or forwards in a line. A line is one-dimensional. If we had two dimensions, on the other hand, we could go forwards and backwards in a line and turn in any direction to start a new line. We are essentially able to travel anywhere on a flat surface. In mathematics, a flat surface is called a plane. A plane is one example of a two-dimensional shape. A plane is essentially the largest sheet of paper you will ever find. In fact, it is a sheet of paper so large that it never ends. One way of thinking about 2D shapes is anything that lays flat on a piece of paper.
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Any n-sided figure, which can be perfectly and wholly traced on a plane is a 2D figure or polygon. This means any figure having all points on a single plane is a planar figure. Some examples are
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### Rectangle
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Number of sides - 4
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Special Info-
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Has four sides, with opposite sides parallel and adjacent sides of same or unequal length(a and b)
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All internal angles are 90 degrees
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Sum of all internal angles in 360 degrees
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Diagonals are mutually perpendicular and bisect one another
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<pre>Area - a * b</pre>
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<pre>Perimeter - 2(a+b)</pre>
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### Square
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Number of sides - 4
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Special Info-
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Has four sides, with opposite sides parallel and all sides of same length (a)
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All internal angles are 90 degrees
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Sum of all internal angles in 360 degrees
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Diagonals are mutually perpendicular and bisect one another
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<pre>Area - a*a</pre>
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<pre>Perimeter - 4*a</pre>
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### Triangle
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Number of sides - 3
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Special Info-
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Has a height which is the perpendicular distance from a vertex to the opposite side(base), can lie inside or outside the triangle
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Sum of all angles is 180 degrees
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<pre>Area - 1/2(base * height)</pre>
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### Circle
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Number of sides - Infinite (A polygon with infinite number of sides is a circle)
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Special Info-
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Angle through center in 360
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Always defined from a point known as center of circle
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Perpendicular distance from the center to a point on periphery is called the radius(r)
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Any line passing through the circle and touching the periphery at both ends is called a chord
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Chord passing through the center of the circle is diameter
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<pre>Area - {pi} * r * r</pre>
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<pre>Perimeter - 2 * {pi} * r </pre>
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#### More Information:
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