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23. Transformations of a Quadrilateral
First, plot the original quadrilateral ABCD.
Vertices: A(-6, -1), B(-6, -4), C(3, -7), D(3, 2).
Plot these points on the grid and connect them to form quadrilateral ABCD.
a) Draw the image A'B'C'D' under enlargement centre (0, -1) scale factor 31.
To find the image coordinates P′(x′,y′) of a point P(x,y) under enlargement with centre E(a,b) and scale factor k, use the formula:
P′(x′,y′)=(a+k(x−a),b+k(y−b))
Given centre E(0,−1) and scale factor k=31.
For A(-6, -1):
A′=(0+31(−6−0),−1+31(−1−(−1)))
A′=(0+31(−6),−1+31(0))
A′=(−2,−1)
For B(-6, -4):
B′=(0+31(−6−0),−1+31(−4−(−1)))
B′=(0+31(−6),−1+31(−3))
B′=(−2,−1−1)
B′=(−2,−2)
For C(3, -7):
C′=(0+31(3−0),−1+31(−7−(−1)))
C′=(0+31(3),−1+31(−6))
C′=(1,−1−2)
C′=(1,−3)
For D(3, 2):
D′=(0+31(3−0),−1+31(2−(−1)))
D′=(0+31(3),−1+31(3))
D′=(1,−1+1)
D′=(1,0)
The coordinates of the image A'B'C'D' are:
A′(−2,−1),B′(−2,−2),C′(1,−3),D′(1,0)
Plot these points and connect them to form quadrilateral A'B'C'D'.
b) Draw A''B''C''D'' the image of A'B'C'D' under rotation of +ve 90° about (1, 0).
To find the image coordinates P′′(x′′,y′′) of a point P′(x′,y′) under a +ve 90° (counter-clockwise) rotation about a centre R(a,b), use the formula:
P′′(x′′,y′′)=(a−(y′−b),b+(x′−a))
Given centre R(1,0).
For A'(-2, -1):
A′′=(1−(−1−0),0+(−2−1))
A′′=(1−(−1),0+(−3))
A′′=(2,−3)
For B'(-2, -2):
B′′=(1−(−2−0),0+(−2−1))
B′′=(1−(−2),0+(−3))
B′′=(3,−3)
For C'(1, -3):
C′′=(1−(−3−0),0+(1−1))
C′′=(1−(−3),0+0)
C′′=(4,0)
For D'(1, 0):
D′′=(1−(0−0),0+(1−1))
D′′=(1−0,0+0)
D′′=(1,0)
The coordinates of the image A''B''C''D'' are:
A′′(2,−3),B′′(3,−3),C′′(4,0),D′′(1,0)
Plot these points and connect them to form quadrilateral A''B''C''D''.
c) Draw A'''B'''C'''D''' the image of A''B''C''D'' under a reflection in the line y−x=0 (i.e., y=x).
To find the image coordinates P′′′(x′′′,y′′′) of a point P′′(x′′,y′′) under reflection in the line y=x, swap the coordinates:
P′′′(x′′′,y′′′)=(y′′,x′′)
For A''(2, -3):
A′′′=(−3,2)
For B''(3, -3):
B′′′=(−3,3)
For C''(4, 0):
C′′′=(0,4)
For D''(1, 0):
D′′′=(0,1)
The coordinates of the image A'''B'''C'''D''' are:
A′′′(−3,2),B′′′(−3,3),C′′′(0,4),D′′′(0,1)
Plot these points and connect them to form quadrilateral A'''B'''C'''D'''.
d) Draw AIVBIVCIVDIV the image of A'''B'''C'''D''' under translation (23) and write the co-ordinate of the final image.
To find the image coordinates PIV(xIV,yIV) of a point P′′′(x′′′,y′′′) under translation by vector (ab), add the translation components to the coordinates:
PIV(xIV,yIV)=(x′′′+a,y′′′+b)
Given translation vector (23).
For A'''(-3, 2):
AIV=(−3+2,2+3)
AIV=(−1,5)
For B'''(-3, 3):
BIV=(−3+2,3+3)
BIV=(−1,6)
For C'''(0, 4):
CIV=(0+2,4+3)
CIV=(2,7)
For D'''(0, 1):
DIV=(0+2,1+3)
DIV=(2,4)
The coordinates of the final image AIVBIVCIVDIV are:
AIV(−1,5),BIV(−1,6),CIV(2,7),DIV(2,4)
Plot these points and connect them to form quadrilateral AIVBIVCIVDIV.
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