Geometric elements (1)

GEOMETRIC ELEMENTS

POLYGONESCIRCLE

ANGLES

LINES

POINTS

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.

ACTIVITY 1

Look this

picture and

create one

using only

points.

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

ACTIVITY 2• USING YOUR SQUARE AND YOUR TRIANGLE

(RULES), DRAW LINES

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.

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

ACTIVITY 3 and 4

• Use the protactor and clasify the angles.

• Draw angles.

• Draw the angle bisector.

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)– …

ACTIVITY

• Using polygons, draw yourself.

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.

ACTIVITY

• Draw a circle using the compass (12 cm of diameter)

• Write the parts of the circle and the circumference.

• Calculate the circumference 2xπxr2