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TWO DIMENSIONAL FIGURES Two dimensional figures are figures that lie on a flat surface, on a plane. For example , a piece of paper. You can draw a 2 dimensional figure on a piece of paper and it lies on a flat surface. Polygons are closed plane figures, they’re closed 2 dimensional figures made up of 3 or more straight Sides, remember that, 3 or more straight sides, Polygons are named by the number of sides they have. For example, polygons that have 3 sides and angles are triangles. There are 3 different types of triangles that you need to know. There is the right triangle, the right triangle has 1 right angle and 2 acute angles, a right angle remember is shown by the square corner. Then we have an acute triangle an acute triangle has 3 acute angles and then we have an obtuse triangle, an obtuse triangle has 1 obtuse angle an 2 acute angles. Then we have polygon with 4 sides and angles these are called QUADRILATERALS and remember we can always use the beginning of our polygons to find how many sides and angles they have. QUAD represents 4, and as we saw earlier triangles TRI represents 3, like a tricycle that has 3 wheels or a tripod to hold a camera has 3 legs a quadrilateral has 4 sides and angles and quad sounds like the Spanish word cuarto which is 4. Lets take a look at our quadrilateral. First we have a parallelogram in a parallelogram opposite sides are equal and parallel, notice how it says opposite sides so this side and this side are equal and this side and this side are equal and both opposite sides are parallel these are parallel to each other and these are parallel to each other that is our parallelogram, then we have a rhombus a rhombus is a parallelogram but all sides are equal it has 4 equal sides so the rhombus takes the definition of a parallelogram opposite sides are equal and parallel yes, but in this one all 4 sides are equal then we have a rectangle a rectangle is a parallelogram with 4 right angles every angle is a right angle we have it says it’s a parallelogram so opposite sides are equal and opposite sides are parallel but in this one there are four right angles which make it a rectangle then we have a square a square is a parallelogram with four equal sides and four right angles, a trapezoid has one pair of parallel sides it is a quadrilateral it has four sides but only one pair are parallel this line and this line are parallel sides, but these two are not parallel then we have an isosceles trapezoid in an isosceles trapezoid there are one pair of parallel sides and this is parallel and this is parallel to each other and 1 pair of equal sides. This side and this side are equal, so we have one pair of parallel sides, one pair of equal sides, and we have an isosceles trapezoid. Polygons that have 5 sides and angles are pentagons, the word Penta means 5. Just like the important building for our government the pentagon has 5 sides. 6 sides and angle are called hexagons. The word Hexa represents 6 and remember the word six has an x and the word hexagon has an x. so hexagons have 6 sides and angles. Polygons with eight sides and angles are called octagons. The word Oct represents 8. Like an octopus that has 8 legs. Or a stop sign is an example of an octagon. Quick tip for two dimensional figures. An easy way to remember what the polygons name is to match it to how many side and angles they have is to remember the prefix and what they mean for each polygon. For example tri angle has 3 sides and angles the prefix tri means 3. Remember a tricycle with three wheels. A quadrilateral has four sides and angles. A quadrilateral has the prefix quad that sounds like the word cuatro. In Spanish which means four. A pentagon which has 5 sides and angles, pent meaning 5, we have a building in the united states that is built like a pentagon and has 5 sides. Then we have a hexagon, a hexagon has 6 sides and angles the prefix hex sounds like six. They both have an x on it so remember hexagon six. And finally we have an octagon. Which has 8 sides and angles the prefix oct means 8 just like octopus which has 8 legs.