SLIDE 1
DAY 12 – IDENTIFYING RIGID
MOTIONS
SLIDE 2 INTRODUCTION When an object is moved from one place to another, its original position changes but the shape and size remains the same. When an object is reflected about a mirror line, it remains at its original position and an image forms
- n the opposite side of the mirror. Having this in
mind among with others, in situations where, the pre-image and the image are given, we can identify a rigid motion that can relate the two. In this topic, we are going to discuss how we can identify the type of rigid motion given two objects.
SLIDE 3
VOCABULARY
Line of symmetry – It is an imaginary line where you can fold an object or image and have two equal and overlapping parts.
SLIDE 4 Reflection To identify a reflection we check whether there
can be a line of symmetry between the two
In the figure above a line of symmetry can be
identified between them. Thus the rigid motion is a reflection
SLIDE 5 Translation To identify whether a rigid motion is a
translation, we check whether the object has been moved to a certain distance and that the object’s shape, size and
- rientation remains the same after being
moved.
In the figure above the two triangles are
equal in size, shape and their orientations are the same. Thus the rigid motion involved is translation.
SLIDE 6 Glide reflection To identify a glide reflection we check whether one
- bject appears to be a reflection of the other which
has been moved by a certain distance. Rectangle B above appears be are a reflection of A which was moved to the right.
B B
SLIDE 7
Rotation To identify a rotation we have to check whether a fixed point can be identified. To do so, we connect at least three lines of an object point with its corresponding image point. When the perpendicular bisector meets at common point, the image would be as a result of rotation.
SLIDE 8
x y 2 6 8 4 10 2 4 6 8 12 10 12 14
SLIDE 9
A fixed point can be identified at (6,1) and the
distance from the object to the fix point remains the same as the distance from the image to the fixed point.
Connecting at least three lines of an object point
with its corresponding image point, then drawing their perpendicular bisectors, we find that they meet at common point, (6,1).
SLIDE 10
HOMEWORK
Identify the rigid motion involved in the set up
below.
SLIDE 11
ANSWERS TO HOMEWORK
1.Translation
SLIDE 12
THE END
