In this lesson, we'll learn words for many different kinds of 2D shapes.
- polygon
- right triangle
- hypotenuse
- equilateral triangle
- isosceles triangle
- obtuse triangle
- acute triangle
- scalene triangle
- trapezoid
- parallelogram
- parallel
- rhombus
A large focus of geometry includes polygons. Polygons are closed 2D shapes with sides made of straight lines. For example, triangles, squares and rectangles are polygons. 3-sided and 4-sided polygons have lots of special names.
3-Sided Shapes
3-sided shapes are called triangles. There are different kinds of triangles. Examine the examples below.
- Right triangles have exactly one right angle (a 90° angle). The longest side of a right triangle (opposite the 90° angle) is called the hypotenuse.
- Equilateral triangles have three equal sides and three equal angles.
- Isosceles triangles have two equal sides and two equal angles.
- Obtuse triangles have one angle that is more than 90°.
- Acute triangles have three angles that are less than 90°.
- Scalene triangles have zero equal sides and angles.
4-Sided Shapes
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