 # (7.7) Geometry and spatial reasoning The student uses coordinate geometry to describe location on a plane. The student is expected to: (B) graph reflections.

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(7.7) Geometry and spatial reasoning The student uses coordinate geometry to describe location on a plane. The student is expected to: (B) graph reflections across the horizontal or vertical axis and graph translations on a coordinate plane. 7.7B Instructional Activity #1

A transformation occurs when a figure is moved by sliding ( ), flipping ( ) or turning ( ). Transformations also occur when the size of a figure is changed by enlarging or reducing a figure to create a similar figure (dilation). Translations, reflections, and dilations can be modeled on a coordinate plane. A figure has been translated, reflected or rotated if it has been moved without changing its shape or size. A figure has been dilated if its size has been changed proportionally. A B C A B C translation A B C reflectionrotation A B C

Reflections A reflection of a figure is its mirror image. A figure is reflected across a line called the line of reflection. The line of reflection serves as the mirror on which the figure is reflected. A figure and its reflected image are always congruent. Each point of the reflected image is the same distance from the line of reflection as the corresponding point of the original figure, but it is on the opposite side of the line of reflection.

If triangle ABC is reflected across the x-axis, what will be the new coordinates of point A ? The coordinates of point A are (____, ____). The x-coordinate of point A is ____. When point A is reflected across the x-axis, its new x-coordinate will still be ____. The y-coordinate of point A is ____. When point A is reflected across the x-axis, its new y- coordinate will be ____. The new coordinates of point A will be (-8, 7). -8-7 -8 -7 7

7.7B STUDENT ACTIVITY #1 If quadrilateral ABCD is reflected across the y-axis, what will be the coordinates of the vertices of the new figure? The coordinates of point A are (_______,_______). After reflecting across the y-axis, the new coordinates of point A will be (_______, _______). The coordinates of point B are (_______,_______). After reflecting across the y-axis, the new coordinates of point B will be (_______, _______). The coordinates of point C are (_______,_______). After reflecting across the y-axis, the new coordinates of point C will be (_______, _______). The coordinates of point D are (_______,_______). After reflecting across the y-axis, the new coordinates of point D will be (_______,_______). 2 3 -2 3 5 8 -5 8 8 5 -8 5 4 -3 -4 -3

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