Mathematics Grade 10 15 min

Classify congruence transformations

Classify congruence transformations

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Introduction & Learning Objectives

Learning Objectives Define a congruence transformation (isometry) and its properties. Identify the four types of congruence transformations: translation, reflection, rotation, and glide reflection. Classify a transformation as a direct or opposite isometry by analyzing the orientation of the figure. Use coordinate rules to describe a specific congruence transformation. Classify a transformation by analyzing the coordinates of a pre-image and its image. Prove two figures are congruent by describing a sequence of congruence transformations that maps one onto the other. Ever wonder how a video game character moves across the screen or how a pattern is created on wallpaper without changing size or shape? 🎮 That's the power of congruence transformations! In this tutorial,...
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Key Concepts & Vocabulary

TermDefinitionExample Congruence Transformation (Isometry)A transformation that preserves distance and angle measure. The pre-image (original figure) and the image (transformed figure) are congruent.Sliding a triangle 5 units to the right. The new triangle is identical in size and shape to the original. TranslationA transformation that slides every point of a figure the same distance in the same direction along a vector.If point P(2, 3) is translated by the vector <4, -1>, its image is P'(6, 2). ReflectionA transformation that flips a figure across a line, called the line of reflection, creating a mirror image.Reflecting the point P(2, 3) across the x-axis results in the image P'(2, -3). RotationA transformation that turns a figure about a fixed point, called the center of...
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Core Formulas

Translation Rule T_{a,b}(x, y) = (x + a, y + b) This rule describes a translation. Every point (x, y) is moved 'a' units horizontally and 'b' units vertically. The vector <a, b> is the translation vector. Reflection Rules Reflection across x-axis: (x, y) -> (x, -y) Reflection across y-axis: (x, y) -> (-x, y) Reflection across line y = x: (x, y) -> (y, x) These rules describe reflections across common lines in the coordinate plane. The sign of one or both coordinates changes, or the coordinates are swapped. Rotation Rules (about the origin) 90° counter-clockwise: (x, y) -> (-y, x) 180°: (x, y) -> (-x, -y) 270° counter-clockwise: (x, y) -> (y, -x) These rules describe counter-clockwise rotations about the origin (0,0). For cl...

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Sample Practice Questions

Challenging
Triangle ABC has vertices A(3, 5), B(7, 5), C(3, 1). Its image has vertices A'(-5, -3), B'(-5, -7), C'(-1, -3). Classify this transformation.
A.glide reflection
B.180° rotation followed by a translation
C.reflection across the y-axis followed by a rotation
D.270° counter-clockwise rotation about the origin
Challenging
A transformation is defined as a reflection across the y-axis followed by a 180° rotation about the origin. What single transformation is equivalent to this sequence?
A.90° counter-clockwise rotation
B.reflection across the x-axis
C.translation
D.reflection across the line y = x
Challenging
To prove that triangle PQR with vertices P(0,0), Q(4,0), R(0,3) is congruent to triangle P'Q'R' with vertices P'(5,2), Q'(1,2), R'(5,5), which sequence of transformations could be used?
A.Translate by vector <5, 2>, then rotate 180° about P'
B.Reflect across the y-axis, then translate by vector <5, 2>
C.Rotate 90° CCW about the origin, then translate by vector <5, 5>
D.Reflect across the line y=x, then translate by vector <2, 1>

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