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GEOMETRY

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BASIC GEOMETRY

Point: A point is a location in space. It is represented by a dot. Point are usually named with a upper case letter. For example, we refer to the following as "point A"

We can also say a point is the intersection of two lines.

Line: A line is a collection of points that extend forever. The following is a line. The two arrows are used to show that it extends forever.

We can also say that a line is the intersection between two planes.

Line segment: A line segment is part of a line. The following is a segment. A segment has two endpoints. The endpoints in the following segments are A and F. Notice also that the line has no endpoints.

GEOMETRY


Ray: A ray is a collection of points that begin at one point (an endpoint) and extend forever on one direction. The following is a ray.

Angle: Two rays with the same endpoint is an angle. The following is an angle.

Plane: A plane is a flat surface like a piece of paper. It extends in all directions. We can use arrows to show that it extends in all directions forever. The following is a plane

RELATIONSHIP BETWEEN TWO STRAIGHT LINES

Two lines can be:

Parallel lines : When two lines never meet in space or on a plane no matter how long we extend them, we say that they are parallel lines The following lines are parallel.

GEOMETRY


Intersecting lines: When lines meet in space or on a plane, we say that they are intersecting lines . The following are intersecting lines.

Perpendicular lines: A line is perpendicular to another if it meets or crosses it at right angles (90°).

TYPES OF LINE

STRAIGHT LINE or CURVED LINE

In geometry when we say line it is a straight line.

POLYGONAL LINE

A broken line composed of a finite number of line segments

GEOMETRY


Types of angles

Type of Angle Description

Acute Angle an angle that is less than 90°

Right Angle an angle that is 90° exactly

Obtuse Angle

an angle that is greater than 90° but less than 180°

Straight Angle an angle that is 180° exactly

Reflex Angle

an angle that is greater than 180° and less than 360o

GEOMETRY


Pairs of Angles

When parallel lines get crossed by another line (which is called

aTransversal), you can see that many angles are the same, as in this

example:

These angles can be made into pairs of angles which have special

names.

Transversal line

Parallel lines

Vertical angles: a=d; c=b; e=h; g=f (Ángulos opuestos por el vértice)

Corresponding angles: a=e; b=f; c=g; h=d (ángulos correspondientes)

c+e =180o ; d+f=180o

a+g= 180o; b+ h=180o

http://www.youtube.com/watch?v=8eD3wODClh8

GEOMETRY


Complementary Angles

Two Angles are Complementary if they add up to 90 degrees (a Right Angle).

These two angles (40° and 50°) are

Complementary Angles, because

they add up to 90°.

Notice that together they make

a right angle.

But the angles don't have to be

together.

These two are complementary

because 27° + 63° = 90°

Supplementary Angles

Two Angles are Supplementary if they add up to 180 degrees.

These two angles (140° and

40°) are Supplementary Angles,

because they add up to 180°.

Notice that together they make

a straight angle.

GEOMETRY


EXERCISES

1. Calculate the value of every complementary angle

2. Plot and find out in every case the complementary angle

3. Match every angle and its complementary one

4. Calculate the value of every suplementary angle

5. Plot and find out in every case the suplementary angle

GEOMETRY


6. Match every angle and its complementary one

7. AB and CD are parallel lines and EH is a transversal. What is the size of angle EFB?

8. AB and CD are parallel lines and EH is a transversal. What is the size of angle DGH?

GEOM

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GEOMETRY


TO BISECT AN ANGLE

1.Con centro en V trazo un arco de circunferencia que corta a los lados del ángulo en 1 y 2 2. Con centro en 1 y radio 12 trazo un arco de circunferencia 3. Con centro en 2 y radio 21 trazo un arco de circunferencia 4. Uno V con el punto que han determinado ambos arcos.

10. Bisect the angles given below:

CIRCUMFERENCES AND CIRCLES

Look at these shapes and think about the difference:

The first and the last are lines and the second and the third are surfaces

How do I call them?

CIRCUMFERENCE: es el lugar geométrico de los puntos del plano que equidistan de un punto llamado centro. A esa distancia se le llama radio

CIRCLE: Es la región del plano delimitada por una circunferencia y que posee un área definida.

GEOMETRY


PARTS OF A CIRCUMFERENCE

11. Name the parts that are drawn in these circumferences.

12. Plot the following circumferences.

GEOMETRY


Polygon: When yhe polygonal line is closed we´ve got a polygon. Polygons are 2‐dimensional

shapes. They are made of straight lines, and the shape is "closed" (all the lines connect up).

Which is a polygon?

The polygons can be

….Concave or Convex

A convex polygon has no angles pointing inwards. More precisely, no internal angles can be more than

180°.

If there are any internal angles greater than 180° then it is concave. (Think: concave has a "cave" in it)

Convex Concave

Regular or Irregular

If all angles are equal and all sides are equal, then it is regular, otherwise it is irregular

Regular Irregular

GEOMETRY


7) The straight lines AB and CD:

A are parallel

B are not parallel because the two given consecutive interior angles do not add to 180°

C are not parallel because the two given corresponding angles are not equal

D are not parallel because the two given alternate angles are not equal

8) AB and CD are parallel lines and EH is a transversal. What is the size of angle EFB?

9) AB and CD are parallel lines and EH is a transversal. What is the size of angle DGH?

GEOMETRY


10) ST and UV are parallel lines. c and e are:

A consecutive interior angles

B alternate angles

C vertical angles

D corresponding angles

11) ST and UV are parallel lines g and f are:


B alternate angles

C vertical angles


12) ST and UV are parallel lines d and e are:


B alternate angles

C vertical angles


13) ST and UV are parallel lines d and h are:


B alternate angles

C vertical angles


14) Two angles are supplementary and one of them is 31° . What is the size of the other angle? 15) Two angles are complementary and one of them is 31° . What is the size of the other angle?

GEOMETRY


10. Plot the following:

A (1,1); B( 4,3); C(3,6); D(9,1); E(7,7)

1. A line passing through point A.

2. Two intersecting lines that intersected in point B

3. A line parallel to the first one

4. A perpendicular line from C to the BC

4. Four different lines passing through point C

5. A ray which vertex is in point D

6. A line segment which one of its endpoints is E

7. An acute angle

8. An obtuse angle

9. A right angle

10. A plane angle

12. Two supplementary angles

13. Two complementary angles

14. Two parallels line and a transversal line and the names of pairs of angles

GEOMETRY


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