Transcript 9-3: Rotations - Mrs. Blondin's Math Zone

9-3: Rotations
Rigor: Students will rotate figures about a point
at increments of 90o.
Relevance: Rotations describe movement.
Rotations defined
• Simply defined: a “turn” about a point of
rotation. (counter-clockwise unless specified)
• Function Notation:
r (xo, Q) (pre-image)
angle of rotation
• Formally Defined: pg 576
point of rotation
Rotating by tracing
This is the easiest way to rotate a figure about
a point
• Use a protractor to draw the angle of rotation
with the point of rotation as the vertex and
one angle side going through the figure’s
vertex
• Trace the figure and the angle
• Turn the figure until one side of the angle
matches up with the other side of the angle
EX 1: Rotating using tracing paper
A) Rotate ∆𝐿𝑂𝐵 100o about point C.
B) r (250o, C) (∆𝐿𝑂𝐵)
Rotations in Regular Polygons
• Recall that a regular polygon has
congruent sides and angles.
• You can divide any regular polygon into
congruent triangles.
• When you rotate a regular polygon
about its center, the sides will line up
when you rotate it a certain number of
degrees, called the central angle.
EX 2
Point X is the center of the regular polygon
PENTA. What is the image for the given
rotation?
A) 72o rotation of E about X.
B) r (216o, X) (𝐸𝑁)
EX 3: Calculating the Angle of Rotation
Rotations in the Coordinate Plane
**This is not in your textbook, write it down!**
EX 4: Rotate FGHI about the origin.
• 90o
• 180o
• 270o
EX 4: Rotate FGHI about the origin.
• 90o
• 180o
• 270o
9-3 Classwork/Homework
• 9-3 classwork: workbook pg 229 #1-6
• Heading: 9-3 Homework pg 580-582
#10-12, 18-24, 32, 44, 48-51
• Due Friday