Angles. Angle and Points An Angle is a figure formed by two rays with a common endpoint, called the...
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Transcript of Angles. Angle and Points An Angle is a figure formed by two rays with a common endpoint, called the...
Angles
Angle and PointsAn Angle is a figure formed by two rays with a
common endpoint, called the vertex.
vertex
ray
rayAngles can have points in the interior, in the exterior or on the angle.
E is in the exterior.
A
BC
DE
Points A, B and C are on the angle.
D is in the interior
B is the vertex.
Naming an Angle
ABC or CBA Using 3 points: Vertex must be the middle letter
This angle can be named as
Using 1 point: Using only vertex letter
A
BC
B
Using a number: 2
2
Use the notation m2, meaning the measure of 2.
Example
K
32
K
L
M
P
Therefore, there is NO in this diagram.
Name all the angles in the diagram below
, ,LKM PKM and LKP
2 3 5!!!There is also and b Nut t Ohere is
K is the vertex of more than one angle.
Example
Name the three angles in the diagram.
4 Types of Angles
Acute Angle: an angle whose measure is less than 90.
Right Angle: an angle whose measure is exactly 90 .
Obtuse Angle: an angle whose measure is between 90 and 180.
Straight Angle: an angle that is exactly 180 .
Angle Addition PostulateSame idea as the segment addition postulate
R
M K
W
The sum of the two smaller angles will always equal the measure of the larger angle.
Complete:
m ____ + m ____ = m _____MRK KRW MRW
Postulate:
Example
Fill in the blanks. m < ______ + m < ______ = m <
_______
Adding Angles
If you add m1 + m2, what is your result?
22°
36°
21
D
B
C
A
Therefore, mADC = 58.
m1 + m2 = mADC
m1 + m2 = 58.
Also…
Example
R
M K
W
3x + x + 6 = 90 4x + 6 = 90 – 6 = –64x = 84x = 21
K is interior to MRW, m MRK = (3x), m KRW = (x + 6) and mMRW = 90º. Find mMRK.
3xx+6
Are we done?
mMRK = 3x = 3•21 = 63º
First, draw it!
ExampleGiven that m< LKN = 145, find m < LKM and m < MKN
ExampleGiven that < KLM is a straight angle, find m < KLN and m < NLM
Example
Given m < EFG is a right angle, find m < EFH and m < HFG
Angle Bisector
An angle bisector is a ray in the interior of an angle that splits the angle into two congruent angles.
5
3
3 5.
Congruent Angles
5
3
Definition: If two angles have the same measure, then they are congruent.
Congruent angles are marked with the same number of “arcs”.
j41°
41°
64
U
K
is an angle bisectorUK
Example:
J
T
Which two angles are congruent?
<JUK and < KUT or < 4 and < 6
Example:Given bisects < XYZ and m < XYW = . Find m < XYZYW
??????????????18
Example:Given bisects < ABC. Find m < ABC
BD??????????????