Using Time to Explore Angles
Geometry Terms to Know
Point - an exact place in space.
A
Line - a straight path between two points that goes
on forever in both directions. A
B
Line Segment - part of a line; has a distinct starting
A
point and ending point.
B
endpoints
Geometry Terms to Know
Ray - part of a line; has a definite starting point, but
no ending point; goes on forever in one direction.
B
D
A
C
Geometry Terms to Know
Angle - formed by two lines, rays, or line segments
that have the same endpoint.
Geometry Terms to Know
Angle - formed by two lines, rays, or line segments
that have the same endpoint. This end point is
called the vertex.
Geometry Terms to Know
We measure angles by measuring the distance
between the two sides of the angle.
Geometry Terms to Know
We measure this distance in a unit called degrees.
The symbol for degrees is a small superscript circle.
Degrees = 45°
Types of Angles
There are essentially three different types of angles.
Let’s use our clocks to discover the names of these
angles.
Right Angles
Set your clock to 3:00.
The hands of the clock form a right angle.
Right Angles
Set your clock to 9:00.
The hands of the clock form a right angle.
Right Angles
Right angles measure
exactly 90 degrees.
Acute Angles
Set your clock to 1:00.
Set your clock to 2:00.
The hands of the clocks form acute angles.
Acute Angles
Set your clock to 10:00.
Set your clock to 11:00.
The hands of the clocks form acute angles.
Acute Angles
Acute angles measure less than 90 degrees.
Straight Angles
Set your clock to 6:00.
The hands of the clock form a straight angle.
Straight Angles
Straight angles measure exactly 180 degrees.
Obtuse Angles
Set your clock to 4:00.
Set your clock to 5:00.
The hands of the clocks form obtuse angles.
Obtuse Angles
Set your clock to 7:00.
Set your clock to 8:00.
The hands of the clocks form obtuse angles.
Obtuse Angles
Obtuse angles measure more than 90 degrees but less than 180 degrees.
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