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Transcript
2D SHAPES and ANGLES What are 2-Dimensional Shapes? A 2-dimensional shape is a geometric figure that has length and width but no thickness or depth. It is a shape that is flat. There are 2Dimensional shapes everywhere! Point to a few of them in the classroom. Triangles Triangles are also considered a type of polygon. It is a three sided shape with three angles. There are different types of triangles. Equilateral Triangles An equilateral triangle is an Isosceles triangle that has 3 sides that are all equal in length. That means that side 1,2 is equal to side 2,3 which is also equal to side 3,1. Isosceles Triangles Isosceles triangles are triangles that have at least 2 sides that are equal in length. It looks different from an equilateral triangle. With a partner, explain how an equilateral triangle looks different from an isosceles triangle. Scalene Triangles A scalene triangle is a triangle that does not have any equal sides. Acute, Obtuse and Right Triangles An acute triangle is a triangle that has 3 angles that measure less than 90 degrees. An obtuse triangle is a triangle that has one angle that measures greater than 90 degrees. A right triangle is a triangle that has one angle that measures exactly 90 degrees. It has one right angle. Measuring Angles Angles can be measured using a tool called a protractor. To measure an angle with a protractor… 1) Place the center of the protractor on the angle's vertex. 2) Rotate the protractor so that the straightedge is placed over one of the angle's sides. 3) Use the scale that begins with zero. Read where the other side of the angle crosses this scale.