Geometry: Plane Shapes

Plane shapes in mathematics are any closed, flat, 2-dimensional shapes. A closed, two-dimensional or flat figure is called a plane shape. Different plane shapes have different attributes, such as the numbers of sides or corners. A side is a straight line that makes part of the shape, and a corner is where two sides meet.  Let’s take a look at some shapes:

As you can see, the plane shapes in the top row include a triangle, rectangle, diamond, and star. The plane shapes in the bottom row include a pentagon (or a 5-sided shape), circle, and square.

Types of Plane Shapes

There are different types of plane shapes? For instance, many plane shapes are polygons, or any 2-dimensional shape with straight sides or lines that is closed and has no open sides. Let’s go back and take another look at the image of the plane shapes and see if any of these shapes are polygons.

That’s right; the triangle, rectangle, diamond, star, pentagon, and square are all polygons.

Another type of plane shape is known as a quadrilateral, or a 2-dimensional shape with 4 straight sides that is closed and has no open sides. Let’s look at some examples of quadrilaterals:

Quadrilaterals Chart

Plane shapes are both polygons and quadrilaterals.

A triangle is a shape with three sides and three corners. A rectangle is a shape with four sides and four corners. They may notice that opposite sides are the same length. A square is a rectangle in which all four sides are of equal length. A circle is a round shape that has no sides or corners.

Properties of Plane Shapes

Plane shapes have properties including sides, corners, and faces.

Triangles

A triangle is a shape with three sides. It can be classified according to its sides or angles, with three kinds each. Here they are:

• Equilateral triangles, which are also equiangular triangles, have three sides equal and three angles equal. Their angles are always 60°.
• Isosceles triangles are triangles in which two of the sides are equal. The non-included angles of the sides are also equal.
• Scalene triangles have no equivalence in any way.
• Right triangles are triangles with a right angle. The longest side of such triangles is called a hypotenuse.
• Obtuse triangles are triangles with an obtuse angle.
• Acute triangles are triangles with no right or obtuse angle….

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GEOMETRY