Post on 10-Jun-2015
description
Introduction to Geometry &
Measurements
Roxanne Joie V. Deang
BSE Math IV
POINTS, LINES, & PLANES
POINTS
Point
basic element in geometry represented by a dot (.)
an idea that shows an exact location in space
no dimension; no length; no width and no thickness
named using a capital letter
LINES
Line
set of infinite points extended endlessly or indefinitely in two directions
represented by a stretch string, edge of a table, etc.
it has one dimension which is the length named by one small letter or two capital
letters
Name this line!
L O V E
PLANES
Plane
set of infinite points extended in four directions
it has two dimensions – length and width represented by any flat surface named by at least three points of the plane
provided that the points must not lie along the same line
Name this
plane!
JV
A
RK
N
D
M
L
RAYS & ANGLES
RAYS
Ray
a part of a line that extends indefinitely in one direction
named by writing the endpoint first and then another point on the ray
R O X
ANGLES
Angle
formed by two rays with a common endpoint the common endpoint is called the
vertex the two rays are called the sides of the
angle
Angle
when naming an angle, the letter designating the vertex should always stand between two other letters.
an angle can also be named by using a single letter designating the vertex
A
B
C
Angle
angles are measured in units called degrees (o)
a protractor is used to measure angles
KINDS OF ANGLES ACCORDING TO MEASUREMENT
RIGHT ANGLE
Right Angle
an angle whose measure is 90o
a small square is usually placed to indicate a right angle
Right Angle
E
D F
ACUTE ANGLE
an angle whose measure is greater than 0o and less than 90o
Acute Angle
Acute Angle
H
G I
OBTUSE ANGLE
Obtuse Angle
an angle whose measure is greater than 90o but less than 180o
Obtuse Angle
K
J L
Try this!
1.) 2
Use the figure to answer each questions below.
What kind of angle is each? Write A for Acute, R for Right and O for Obtuse.
12 3
4A
B CD
E
2.) 4
3.) 1 + 2
4.) 2 + 3
5.) 2 + 3 + 4
6.) 1 + 2 + 3
A1
A2
R3
O4
O5
O6