Notes 1.4 Angle Measures. LT – I can find and compare angle measures. Definition of an Angle. Angle – formed by two rays with the same endpoint . The rays are the sides or legs of the angle and the endpoint is the vertex. vertex. A. Naming an Angle.
LT – I can find and compare angle measures.
Angle – formed by two rays with the same endpoint. The rays are the sides or legs of the angle and the endpoint is the vertex.
A. Naming an Angle
The name can be the numberbetween the sides of the angle: /3.
The name can be the vertexof the angle: /G.
The name can be three points that include on each ray with the vertex
written in the middle/AGCor / CGA.
/ 1 by NUMBER
/ ABC by POINTS with vertex in the middle
/ B by VERTEX point
These angles are called “adjacent” which means “next to” because they share a ray.
/ POR &
NOT / ORQ ,
Right = 90
Acute < 90
Straight = 180
Obtuse > 90
Example 1 Suppose that m/1 = 42 and m/ ABC= 88. Find m/2.
m/1 + m/2 = m/ ABC
42 + m/2 = 88
m/2 = 46
Angles with the same measure are congruent. Congruent angles are marked by arcs.
Example 1 Find m/GXF and m/IXJ
5x + 3 = 7x – 9
3 = 2x – 9
12 = 2x
6 = x
m/GXF = 5(6) + 3 = 33°
m/IXJ = 7(6) – 9 = 33°
7x - 9
5x + 3
You need to make sure the protractor is lined up correctly.
Is this ready to measure the angle?
Look for the upside down ‘T’ in the middle of the straight line on your protractor.
This needs to be exactly on the vertex of your angle.
way round the
angle is, you
to line the upside
down ‘T’ to the vertex
of the angle.
Read from the 0°, and follow the inner set of numbers.
You then need to look at the 1° markings on the outer set of numbers.
This angle measures 35°.