Download Lesson 16-2

LINE SEGMENTS, RAYS, AND ANGLES
Lesson 16-2
CCSS 4.G.1
How can lines, angles,
and shapes be described,
analyzed, and classified?
How are angles
measured, added, and
subtracted?
WARM UP
 A carton of eggs has 12 eggs. Greg used 1/3 of
his carton of eggs to make breakfast. Trisha
used ¼ of her carton of eggs for breakfast.
Who used more eggs, Greg or Trisha? Explain.
TODAY’S LESSON
In this lesson, you will identify and name line
segments, rays, and angles.
Let’s look at the Envision Video for this lesson
and take the quiz.
LINE SEGMENTS - VOCABULARY
A line segment is a part of a line with two
endpoints. Segments do not go on forever like lines
do. Line segments are named by the letters on their
two endpoints.
J
K
MORE VOCABULARY
Ray: A type of line that begins at a point and goes
on forever in one direction.
Angle: Two rays that meet at the same endpoint
Vertex: The point where 2 rays meet (and form an
angle).
RIGHT ANGLES
Right Angle: An angle that makes a square corner.
Use craft sticks to make a right angle.
ACUTE ANGLES
Acute angle: An angle that is open less than a right
angle (with its rays closer together).
You can remember that an acute angle’s opening is
littler than a right angle because it is “a cute little
angle”.
Use craft sticks to make an acute angle.
OBTUSE ANGLES
Obtuse angle: An angle that has an opening bigger
than a right angle (with its rays farther apart).
Memory Trick! An obtuse angle is big, and obtuse
sounds like obese (which means big). It’s an obtuse
obese angle!
Use craft sticks to make an obtuse angle.
PRACTICE!
Draw an acute angle in your notebook.
Draw a right angle in your notebook.
Draw an obtuse angle in your notebook.
NAME THAT ANGLE!
THINK AND WRITE
Think of a clock. Give an example of a time that the
clock’s hands make a right angle. Give an example
of a time the clock’s hands make an obtuse angle,
and a time the clock’s hands make an acute angle.
ANGLES SONGS
https://www.youtube.com/watch?v=qHB2vVHAjpg
LESSON WRAP UP
In this lesson, you learned that line segments and rays can help
describe parts of lines and geometric shapes. You also learned
angles are formed by two intersecting lines and classified by size.
Homework (16-2 Practice) for one “Paw Signature” and (16-2
Reteaching & Practice) if you want two “Paw Signatures.”
Website for Practice:
http://www.sheppardsoftware.com/mathgames/geometry/shape
shoot/line_shoot.htm