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# Geometric elements (1)

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created by Maria Jose Aparicio

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### Geometric elements (1)

1. 1. GEOMETRIC ELEMENTS POLYGONES CIRCLE ANGLES LINES POINTS
2. 2. POINTS • We may think of a point as a “dot” on a piece of paper. • We identify this point with a number or a CAPITAL letter. • A point has no length or width, it just specifies an exact location.
3. 3. ACTIVITY 1 Look this picture and create one using only points.
4. 4. LINES • STRAIGHT LINES don’t have a begginig or an end. • RAYS has a beginning point but it hasn’t an end point. • LINE SEGMENT has a beginning point and an end point. • CURVE LINES • POLYGONAL LINES • PARALLEL LINES • SECANT STRAIGHT LINES • PERPENDICULAR LINES
5. 5. ACTIVITY 2 • USING YOUR SQUARE AND YOUR TRIANGLE (RULES), DRAW LINES
6. 6. ANGLES • Two rays that share the same endpoint, called vertex. • Clasification by measurement: – Acute<90º – Right =90º – Obtuse>90º – Flat =180º – Full =360º • We use the protactor.
7. 7. ANGLES • ANGLE BISECTOR is a ray that divides an angle into two equal angles. – Place the compasses' point on the angle's vertex. – Adjust the compasses to a medium wide setting. The exact width is not important. – Without changing the compasses' width, draw an arc across each leg of the angle. – Place the compasses on the point where one arc crosses a leg and draw an arc in the interior of the angle. – Without changing the compasses setting repeat for the other leg so that the two arcs cross. – Using a straightedge or ruler, draw a line from the vertex to the point where the arcs cross How to make it
8. 8. ACTIVITY 3 and 4 • Use the protactor and clasify the angles. • Draw angles. • Draw the angle bisector.
9. 9. POLYGONS • A polygon is a closed figure made by joining line segments. • Polygons can be regular or irregular; o, . – Triangles (3 sides) – Quadrilateral (4 sides) – Pentagon (5 sides) – Hexagon (6 sides) – Heptagon (7 sides) – …
10. 10. ACTIVITY • Using polygons, draw yourself.
11. 11. CIRCLE • Radius: it’s the distance from the center of the circle to the outside edge. • Diameter: it’s the longest distance across a circle. • Circumference: it’s the perimeter, the distance around the outer edge. • Chord: it’s a line segment that connects one point on the edge of the circle with another point on the circle. • Arc: it’s a segment of the circumference of the circle. • Sector: it’s a pie shaped portion of the área of the circle.
12. 12. ACTIVITY • Draw a circle using the compass (12 cm of diameter) • Write the parts of the circle and the circumference. • Calculate the circumference  2xπxr2