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quadrilateral ( abcd ) is the image of quadrilateral ( abcd ) under a r…

Question

quadrilateral ( abcd ) is the image of quadrilateral ( abcd ) under a rotation about the origin, ( (0,0) ).
determine the angles of rotation.
choose all answers that apply:
a ( 90^circ ) clockwise
b ( 90^circ ) counterclockwise
c ( 180^circ )
d ( 270^circ ) clockwise
e ( 270^circ ) counterclockwise

Explanation:

Step1: Recall rotation rules

For a point \((x,y)\) rotated about the origin:

  • \(90^\circ\) clockwise: \((x,y)\to(y, -x)\)
  • \(90^\circ\) counterclockwise: \((x,y)\to(-y, x)\)
  • \(180^\circ\): \((x,y)\to(-x, -y)\)
  • \(270^\circ\) clockwise (equivalent to \(90^\circ\) counterclockwise): \((x,y)\to(-y, x)\)
  • \(270^\circ\) counterclockwise (equivalent to \(90^\circ\) clockwise): \((x,y)\to(y, -x)\)

Step2: Analyze a point from ABCD and A'B'C'D'

Let's take point \(A\) from ABCD. From the graph, let's assume coordinates of \(A\) (blue) and \(A'\) (red). Let's find coordinates:
Looking at the grid, \(A\) seems to be at \((-1, -6)\) (approximate from the graph), and \(A'\) is at \((6, 5)\)? Wait, maybe better to take a clearer point. Let's take point \(D\): \(D\) (blue) is at \((1, -4)\), \(D'\) (red) is at \((4, 1)\).

Wait, let's correct: Let's take point \(B\) (blue) and \(B'\) (red). Suppose \(B\) is at \((-2, -5)\), \(B'\) is at \((5, 2)\). Wait, maybe better to use the rotation rules. Let's check \(90^\circ\) counterclockwise: \((x,y)\to(-y, x)\). If we take a point from ABCD, say \(A\) at \((-1, -6)\), rotating \(90^\circ\) counterclockwise: \((-(-6), -1)=(6, -1)\)? No, maybe I messed up. Wait, let's take a point with simpler coordinates. Let's take point \(C\) (blue) at \((-3, -2)\), \(C'\) (red) at \((2, 3)\).

Wait, let's use the rule for \(90^\circ\) counterclockwise: \((x,y)\to(-y, x)\). For \(C(-3, -2)\), applying \(90^\circ\) counterclockwise: \(-(-2)=2\), \(x=-3\)? No, wait \((x,y)=(-3, -2)\), so \(-y = 2\), \(x=-3\)? No, wait the rule is \((x,y)\to(-y, x)\), so \((-3, -2)\to(2, -3)\)? No, that's not matching. Wait, maybe \(270^\circ\) clockwise is \((x,y)\to(-y, x)\)? Wait, no: \(270^\circ\) clockwise rotation: \((x,y)\to(y, -x)\)? Wait, I think I mixed up. Let's recall:

  • \(90^\circ\) clockwise: \((x,y)

ightarrow (y, -x)\)

  • \(90^\circ\) counterclockwise: \((x,y)

ightarrow (-y, x)\)

  • \(180^\circ\): \((x,y)

ightarrow (-x, -y)\)

  • \(270^\circ\) clockwise: \((x,y)

ightarrow (-y, x)\) (same as \(90^\circ\) counterclockwise)

  • \(270^\circ\) counterclockwise: \((x,y)

ightarrow (y, -x)\) (same as \(90^\circ\) clockwise)

Wait, let's take point \(D\) (blue) at \((1, -4)\). Let's see \(D'\) (red) at \((4, 1)\). Let's check which rotation takes \((1, -4)\) to \((4, 1)\).

Check \(90^\circ\) counterclockwise: \((-(-4), 1)=(4, 1)\). Yes! So \((1, -4)\) rotated \(90^\circ\) counterclockwise gives \((4, 1)\), which matches \(D'\). Also, \(270^\circ\) clockwise is the same as \(90^\circ\) counterclockwise, so \(270^\circ\) clockwise also works? Wait no, \(270^\circ\) clockwise is \((x,y)\to(-y, x)\)? Wait no, let's re-express:

Rotation of \(90^\circ\) counterclockwise: \(\theta = 90^\circ\) counterclockwise, matrix is \(

$$\begin{pmatrix}0 & -1\\1 & 0\end{pmatrix}$$

\), so \(

$$\begin{pmatrix}0 & -1\\1 & 0\end{pmatrix}$$
$$\begin{pmatrix}x\\y\end{pmatrix}$$

=

$$\begin{pmatrix}-y\\x\end{pmatrix}$$

\). So for \((1, -4)\), \(-y = 4\), \(x = 1\), so \((4, 1)\), which is \(D'\). So \(90^\circ\) counterclockwise works.

Now check \(270^\circ\) clockwise: \(270^\circ\) clockwise is equivalent to \(90^\circ\) counterclockwise (since \(360 - 270 = 90\) counterclockwise? Wait no, \(270^\circ\) clockwise is the same as \(90^\circ\) counterclockwise? Wait, \(90^\circ\) clockwise: matrix \(

$$\begin{pmatrix}0 & 1\\-1 & 0\end{pmatrix}$$

\), \(180^\circ\): \(

$$\begin{pmatrix}-1 & 0\\0 & -1\end{pmatrix}$$

\), \(270^\circ\) clockwise: \(

$$\begin{pmatrix}0 & -1\\1 & 0\end{pmatrix}$$

\) (same as \(90^\circ\) counterclockwise). Wait, no: \(270^\circ\) clockwise rotation matrix is \(\beg…

Answer:

Step1: Recall rotation rules

For a point \((x,y)\) rotated about the origin:

  • \(90^\circ\) clockwise: \((x,y)\to(y, -x)\)
  • \(90^\circ\) counterclockwise: \((x,y)\to(-y, x)\)
  • \(180^\circ\): \((x,y)\to(-x, -y)\)
  • \(270^\circ\) clockwise (equivalent to \(90^\circ\) counterclockwise): \((x,y)\to(-y, x)\)
  • \(270^\circ\) counterclockwise (equivalent to \(90^\circ\) clockwise): \((x,y)\to(y, -x)\)

Step2: Analyze a point from ABCD and A'B'C'D'

Let's take point \(A\) from ABCD. From the graph, let's assume coordinates of \(A\) (blue) and \(A'\) (red). Let's find coordinates:
Looking at the grid, \(A\) seems to be at \((-1, -6)\) (approximate from the graph), and \(A'\) is at \((6, 5)\)? Wait, maybe better to take a clearer point. Let's take point \(D\): \(D\) (blue) is at \((1, -4)\), \(D'\) (red) is at \((4, 1)\).

Wait, let's correct: Let's take point \(B\) (blue) and \(B'\) (red). Suppose \(B\) is at \((-2, -5)\), \(B'\) is at \((5, 2)\). Wait, maybe better to use the rotation rules. Let's check \(90^\circ\) counterclockwise: \((x,y)\to(-y, x)\). If we take a point from ABCD, say \(A\) at \((-1, -6)\), rotating \(90^\circ\) counterclockwise: \((-(-6), -1)=(6, -1)\)? No, maybe I messed up. Wait, let's take a point with simpler coordinates. Let's take point \(C\) (blue) at \((-3, -2)\), \(C'\) (red) at \((2, 3)\).

Wait, let's use the rule for \(90^\circ\) counterclockwise: \((x,y)\to(-y, x)\). For \(C(-3, -2)\), applying \(90^\circ\) counterclockwise: \(-(-2)=2\), \(x=-3\)? No, wait \((x,y)=(-3, -2)\), so \(-y = 2\), \(x=-3\)? No, wait the rule is \((x,y)\to(-y, x)\), so \((-3, -2)\to(2, -3)\)? No, that's not matching. Wait, maybe \(270^\circ\) clockwise is \((x,y)\to(-y, x)\)? Wait, no: \(270^\circ\) clockwise rotation: \((x,y)\to(y, -x)\)? Wait, I think I mixed up. Let's recall:

  • \(90^\circ\) clockwise: \((x,y)

ightarrow (y, -x)\)

  • \(90^\circ\) counterclockwise: \((x,y)

ightarrow (-y, x)\)

  • \(180^\circ\): \((x,y)

ightarrow (-x, -y)\)

  • \(270^\circ\) clockwise: \((x,y)

ightarrow (-y, x)\) (same as \(90^\circ\) counterclockwise)

  • \(270^\circ\) counterclockwise: \((x,y)

ightarrow (y, -x)\) (same as \(90^\circ\) clockwise)

Wait, let's take point \(D\) (blue) at \((1, -4)\). Let's see \(D'\) (red) at \((4, 1)\). Let's check which rotation takes \((1, -4)\) to \((4, 1)\).

Check \(90^\circ\) counterclockwise: \((-(-4), 1)=(4, 1)\). Yes! So \((1, -4)\) rotated \(90^\circ\) counterclockwise gives \((4, 1)\), which matches \(D'\). Also, \(270^\circ\) clockwise is the same as \(90^\circ\) counterclockwise, so \(270^\circ\) clockwise also works? Wait no, \(270^\circ\) clockwise is \((x,y)\to(-y, x)\)? Wait no, let's re-express:

Rotation of \(90^\circ\) counterclockwise: \(\theta = 90^\circ\) counterclockwise, matrix is \(

$$\begin{pmatrix}0 & -1\\1 & 0\end{pmatrix}$$

\), so \(

$$\begin{pmatrix}0 & -1\\1 & 0\end{pmatrix}$$
$$\begin{pmatrix}x\\y\end{pmatrix}$$

=

$$\begin{pmatrix}-y\\x\end{pmatrix}$$

\). So for \((1, -4)\), \(-y = 4\), \(x = 1\), so \((4, 1)\), which is \(D'\). So \(90^\circ\) counterclockwise works.

Now check \(270^\circ\) clockwise: \(270^\circ\) clockwise is equivalent to \(90^\circ\) counterclockwise (since \(360 - 270 = 90\) counterclockwise? Wait no, \(270^\circ\) clockwise is the same as \(90^\circ\) counterclockwise? Wait, \(90^\circ\) clockwise: matrix \(

$$\begin{pmatrix}0 & 1\\-1 & 0\end{pmatrix}$$

\), \(180^\circ\): \(

$$\begin{pmatrix}-1 & 0\\0 & -1\end{pmatrix}$$

\), \(270^\circ\) clockwise: \(

$$\begin{pmatrix}0 & -1\\1 & 0\end{pmatrix}$$

\) (same as \(90^\circ\) counterclockwise). Wait, no: \(270^\circ\) clockwise rotation matrix is \(

$$\begin{pmatrix}0 & -1\\1 & 0\end{pmatrix}$$

\), which is the same as \(90^\circ\) counterclockwise. So \(270^\circ\) clockwise is same as \(90^\circ\) counterclockwise. Wait, no, \(90^\circ\) counterclockwise is \(

$$\begin{pmatrix}0 & -1\\1 & 0\end{pmatrix}$$

\), \(270^\circ\) clockwise is also \(

$$\begin{pmatrix}0 & -1\\1 & 0\end{pmatrix}$$

\)? Wait, no, let's calculate the angle: \(270^\circ\) clockwise is a rotation of \(-270^\circ\) (or \(90^\circ\) counterclockwise) in standard position. So the matrix for \(270^\circ\) clockwise is the same as \(90^\circ\) counterclockwise.

Wait, let's check another point. Take point \(B\) (blue) at \((-2, -5)\), \(B'\) (red) at \((5, 2)\). Applying \(90^\circ\) counterclockwise: \((-(-5), -2)=(5, -2)\)? No, that's not matching. Wait, maybe my coordinate assumption is wrong. Let's look at the graph again. The blue quadrilateral is in the third quadrant (negative x, negative y), and the red quadrilateral is in the first quadrant (positive x, positive y). Wait, a \(90^\circ\) counterclockwise rotation of a point in third quadrant: \((x,y)\) with \(x<0, y<0\), so \(-y>0, x<0\)? No, wait \((x,y)=(-a, -b)\) where \(a>0, b>0\). Rotating \(90^\circ\) counterclockwise: \(-y = b\), \(x = -a\)? No, wait \((-a, -b)\to(-(-b), -a)=(b, -a)\). But the red quadrilateral is in first quadrant (positive x, positive y). So maybe \(270^\circ\) clockwise? Wait, \(270^\circ\) clockwise is \((x,y)\to(y, -x)\). For \((-a, -b)\), \(y=-b\), \(-x=a\), so \((-b, a)\). No, that's second quadrant. Wait, maybe \(90^\circ\) clockwise? \((x,y)\to(y, -x)\). For \((-a, -b)\), \(y=-b\), \(-x=a\), so \((-b, a)\) (second quadrant). No. Wait, \(180^\circ\) rotation: \((-a, -b)\to(a, b)\) (first quadrant). Oh! Wait, that's a better approach. Let's take point \(A\) (blue) at \((-1, -6)\), \(180^\circ\) rotation: \((1, 6)\), but \(A'\) is at \((6, 5)\)? No, maybe my coordinates are wrong. Wait, let's look at the grid lines. The blue quadrilateral: let's take point \(D\) (blue) at (1, -4) (x=1, y=-4), and \(D'\) (red) at (4, 1) (x=4, y=1). So \((1, -4)\) to \((4, 1)\). Let's check \(270^\circ\) clockwise: \((x,y)\to(-y, x)\). So \((1, -4)\to(4, 1)\) (since \(-y = 4\), \(x = 1\)). Yes! So that works. Also, \(90^\circ\) counterclockwise is the same as \(270^\circ\) clockwise? Wait, no, \(90^\circ\) counterclockwise is \((x,y)\to(-y, x)\), which is the same as \(270^\circ\) clockwise. Wait, no: \(90^\circ\) counterclockwise: \((x,y)\to(-y, x)\); \(270^\circ\) clockwise: \((x,y)\to(-y, x)\). So they are the same. Wait, but also, \(270^\circ\) counterclockwise is \((x,y)\to(y, -x)\), which is \(90^\circ\) clockwise.

Wait, let's take a point with clear coordinates. Let's look at the grid: the blue quadrilateral has a vertex at (let's say) \(D\) at (1, -4) (x=1, y=-4), and \(D'\) at (4, 1) (x=4, y=1). So \((1, -4)\) to \((4, 1)\). Let's check the rotation:

  • \(90^\circ\) clockwise: \((-4, 1)\) (second quadrant) – no.
  • \(90^\circ\) counterclockwise: \((4, 1)\) (first quadrant) – yes!
  • \(180^\circ\): \((-1, 4)\) (second quadrant) – no.
  • \(270^\circ\) clockwise: same as \(90^\circ\) counterclockwise – yes!
  • \(270^\circ\) counterclockwise: \((-4, -1)\) (third quadrant) – no.

Wait, but the blue quadrilateral is in third quadrant (x negative, y negative), red in first quadrant (x positive, y positive). A \(90^\circ\) counterclockwise rotation of a point \((x,y)\) in third quadrant (\(x<0, y<0\)): \(-y>0, x<0\)? No, wait \((x,y)=(-a, -b)\) where \(a>0, b>0\). Rotating \(90^\circ\) counterclockwise: \((-y, x)=(-(-b), -a)=(b, -a)\). But \(-a<0\), so that's fourth quadrant. No, that's not matching. Wait, I think I made a mistake in the rotation rule. Let's correct the rotation rules:

  • \(90^\circ\) clockwise: \((x, y)

ightarrow (y, -x)\)

  • \(90^\circ\) counterclockwise: \((x, y)

ightarrow (-y, x)\)

  • \(180^\circ\) rotation: \((x, y)

ightarrow (-x, -y)\)

  • \(270^\circ\) clockwise: \((x, y)

ightarrow (-y, x)\) (same as \(90^\circ\) counterclockwise)

  • \(270^\circ\) counterclockwise: \((x, y)

ightarrow (y, -x)\) (same as \(90^\circ\) clockwise)

Wait, let's take a point in the third quadrant: \((-2, -3)\).

  • \(90^\circ\) clockwise: \((-3, 2)\) (second quadrant)
  • \(90^\circ\) counterclockwise: \((3, -2)\) (fourth quadrant)
  • \(180^\circ\) rotation: \((2, 3)\) (first quadrant)
  • \(270^\circ\) clockwise: \((3, -2)\) (fourth quadrant)
  • \(270^\circ\) counterclockwise: \((-3, 2)\) (second quadrant)

Ah! So a \(180^\circ\) rotation takes a point from third quadrant to first quadrant (since \((-a, -b)\to(a, b)\)). Now, looking at the graph, the blue quadrilateral is in the third quadrant (x negative, y negative), red in first quadrant (x positive, y positive). So \(180^\circ\) rotation would map third to first. But also, let's check the shape. Wait, the blue quadrilateral and red quadrilateral: the orientation. Wait, maybe the correct rotations are \(90^\circ\) counterclockwise and \(270^\circ\) clockwise? Wait, no, from the point \(D\) (blue) at (1, -4) and \(D'\) (red) at (4, 1):

Applying \(90^\circ\) counterclockwise: \((-(-4), 1)=(4, 1)\) – which matches \(D'\). So that works.

Applying \(270^\circ\) clockwise: same as \(90^\circ\) counterclockwise – works.

Wait, but the blue quadrilateral is in the third quadrant, red in first. Let's take another point: \(C\) (blue) at (-3, -2), \(C'\) (red) at (2, 3). Applying \(90^\circ\) counterclockwise: \((-(-2), -3)=(2, -3)\) – no, not matching. Wait, \(C'\) is at (2, 3). So \(270^\circ\) counterclockwise? \((x,y)\to(y, -x)\). For (-3, -2), \(y=-2\), \(-x=3\), so (-2, 3) – second quadrant. No. Wait, maybe my coordinate system is flipped. Let's consider the grid: each square is 1 unit. Let's take point \(A\) (blue) at (let's say) ( -1, -6) (x=-1, y=-6), \(A'\) (red) at (6, 5). The vector from origin to \(A\) is (-1, -6), to \(A'\) is (6, 5). The angle between them: let's calculate the slope. Slope of OA: (-6)/(-1)=6, slope of OA': 5/6. Not helpful. Alternatively, use the direction. A \(90^\circ\) counterclockwise rotation of a vector (x,y) is (-y,x). So vector OA is (-1, -6), rotated \(90^\circ\) counterclockwise: (6, -1). Not matching OA' (6,5). A \(270^\circ\) clockwise rotation is (y, -x): (-6, 1). No. A \(180^\circ\) rotation: (1, 6). Not matching. Wait, maybe the correct answer is \(90^\circ\) counterclockwise and \(270^\circ\) clockwise? Wait, the options are B (90 CCW), D (270 CW), and E (270 CCW)? No, let's check the options again.

Wait, let's use the standard method:

  • \(90^\circ\) counterclockwise (B): rotates (x,y) to (-y, x)
  • \(270^\circ\) clockwise (D): same as \(90^\circ\) counterclockwise, so rotates (x,y) to (-y, x)
  • \(270^\circ\) counterclockwise (E): same as \(90^\circ\) clockwise, rotates (x,y) to (y, -