Chapter 4 Section 3 - Notes
Name ____________________
Date Due _________________
Period _________
Rotations
Vocabulary:
Rotation

a transformation in which a figure is turned about a fixed point called the center of
rotation

rays drawn from the center of rotation to a point and its image form the angle of
rotation

a rotation about a point P through an angle of x° maps every point Q in the plane to a
point Q′ so that one of the following properties is true:
If Q is not the center of rotation P, then QP = Q′P and m∠QPQ′ = x°
If Q is the center of rotation P, then Q = Q′

You can rotate a figure more than 180°

the diagram shows rotations of point A 130°, 220°, and 310° about the origin

point A and its images all lie on the same circle

a rotation of 360° maps a figure onto itself

use coordinate rules to find the coordinates of a point after a rotation of 90°, 180°, or
270° about the origin
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Chapter 4 Section 3 - Notes
Name ____________________
Date Due _________________
Period _________
Coordinate Rules for Rotations about the Origin

when a point (a, b) is rotated counterclockwise about the origin,
the following are true:
For a rotation of 90°, (a, b)
(−b, a)
For a rotation of 180°, (a, b)
(−a, −b)
For a rotation of 270°, (a, b)
(b, −a)
Rotational Symmetry

when the figure can be mapped onto itself by a rotation of 180° or less about the center
of the figure. This point is the center of symmetry

the rotation can be either clockwise or counterclockwise
Example:
The regular octagon has rotational symmetry. The
center is the intersection of the diagonals. Rotations of
45°, 90°, 135°, or 180° about the center all map the
octagon onto itself. The regular octagon also has point
symmetry, which is 180° rotational symmetry

For a figure with s lines of symmetry, the smallest rotation that maps the figure onto
itself has the measure 360°/s
Example:
The triangle has line symmetry
Three lines of symmetry can be drawn for the figure
The equilateral triangle has 360°/3 or 120° rotational
symmetry
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Chapter 4 Section 3 - Notes
Name ____________________
Date Due _________________
Period _________
Example 1:
Rotating a Figure in the Coordinate Plane
Graph quadrilateral RSTU with vertices R(3, 1), S(5, 1),
T(5, −3), and U(2, −1) and its image after a 270° rotation
about the origin.
R’ = _____________
S’ = _____________
T’ = _____________
U’ = _____________
Example 2:
Graph ΔABC with vertices A(3, 1), B(3, 4), and C(1, 1) and its image after a 180° rotation
about the origin.
A’ = _____________
B’ = _____________
C’ = _____________
Page 3 of 6
Chapter 4 Section 3 - Notes
Name ____________________
Date Due _________________
Period _________
Example 3: Performing a Composition
Graph RS with endpoints R(1, −3) and S(2, −6) and its image after the composition.
Reflection:
in the y-axis
Rotation:
90° about the origin
R’ = ________
S’ = ________
R’’ = ________
S’’ = ________
Example 4:
Graph ΔTUV with vertices T(1, 2), U(3, 5), and V(6, 3) and its image after the composition
Rotation:
180° about the origin
Reflection:
in the x-axis
T’ = ________
U’ = ________
V’ = ________
T’’ = ________
U’’ = ________
V’’ = ________
Page 4 of 6
Chapter 4 Section 3 - Notes
Name ____________________
Date Due _________________
Period _________
Example 5: Identifying Rotational Symmetry
Does the figure have rotational symmetry? If so, describe any rotations that map the
figure onto itself.
a. Parallelogram
b. Trapezoid
Rotational Symmetry? Yes/No
Rotational Symmetry? Yes/No
# of degrees = ___________
# of degrees = ___________
c. Dodecagon
d. Octagon
Rotational Symmetry? Yes/No
Rotational Symmetry? Yes/No
# of degrees = ___________
# of degrees = ___________
e. Right Scalene Triangle
f. Arrow
Rotational Symmetry? Yes/No
Rotational Symmetry? Yes/No
# of degrees = ___________
# of degrees = ___________
Page 5 of 6
Chapter 4 Section 3 - Notes
Name ____________________
Date Due _________________
Period _________
g. Isosceles Triangle
h. Basketball
Rotational Symmetry? Yes/No
Rotational Symmetry? Yes/No
# of degrees = ___________
# of degrees = ___________
i. Guitar
j. Card
Rotational Symmetry? Yes/No
Rotational Symmetry? Yes/No
# of degrees = ___________
# of degrees = ___________
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