Transcript LESSON 1 NATURE AND ESSENCE OF GEOMETRY

ANGLE
• A FIGURE FORMED BY
TWO NONCOLLINEAR
RAYS WITH A
COMMON ENDPOINT.
ANGLE
• The TWO
NONCOLLINEAR
RAYS (ray BP &
ray BC) are the
SIDES
angle.
of an
ANGLE
• The point
where the rays
intersect is
called the
VERTEX of
an angle.
ANGLE MNEMONIC
• S- Sides are 2 non-collinear rays.
• E- Endpoint is also called vertex.
• R- Rays are the 2 sides.
• V- Vertex is the common endpoint.
AN ANGLE SEPARATES A
PLANE INTO 3 PARTS
• INTERIOR ANGLE- point D
• EXTERIOR ANGLE – point H
• THE ANGLE ITSELF
P, A, W,C
●H
●D
EXAMPLES
An angle is named by:
1.USING
3 POINTS.
EXAMPLE:
ABC
orCBA
PBW or
WBP
An angle is named by:
2. BY THE
VERTEX
ALONE.
EXAMPLE:
B
An angle is named by:
3. BY USING
A NUMERAL.
EXAMPLE:
1
1
1
EXERCISES
3
2
1
NAMETHE
THEANGLES
ANGLES
NAME
USING3APOINTS
NUMERAL
USING
3
2
1
WHAT
ARE
THE
SIDES
OF
ANOTHER NAME OF
ANGLE
3.
ANGLE 1.
B or
ABW
Segment
PBC or
3
AC and
ABC
2
ray AP
AP
1
WHAT IS THE COMMON
SIDE OF 2 AND 3?
Segment
AC
1
3
2
EXAMPLE 5
Name angles
Name the three angles in the diagram.
WXY, or
YXW
YXZ, or
ZXY
WXZ, or
ZXW
You should not name any of these angles
angles have X as their vertex.
X because all three
Degrees: Measuring Angles
Angles are measured in units
called DEGREES and
classified according to their
measures.
Acute Angles
an angle measuring between
0 and 90 degrees
Obtuse Angles
an angle measuring between
90 and 180 degrees
Right Angles
an angle measuring exactly
90 degrees.
Obtuse Angles
an angle measuring between
90 and 180 degrees
Degrees: Measuring Angles
We measure the size of an
angle using a device called
the PROTRACTOR.
HOW TO USE A PROTRACTOR
Use a protractor for exercises 1-2
 Construct
an angle with a measure
of 45 degrees.
 Construct an angle with measure of
125 degrees.
QUIZ
 1.
NAME THE
ANGLES USING 3
POINTS.
 2. WHAT ARE THE
SIDES OF PAR?
 3. WHAT IS THE
VERTEX OF DAR?
D
P
A
R
HOMEWORK
WHAT IS A POLYGON?
 WHAT ARE THE TYPES OF
POLYGON?
