QUESTION IMAGE
Question
name
geometry
1 write a single translation that is equivalent to ( t _ { 3, - 1 } ) followed by ( t _ { - 5,5 } ).
2 if the coordinates of point ( p ) are ( ( 2, - 3 ) ), then ( ( r _ { 90 } circ r _ { 180 } ) ( p ) ) is
- ( ( - 2,3 ) ) 2) ( ( - 2, - 3 ) ) 3) ( ( 3, - 2 ) ) 4) ( ( - 3, - 2 ) )
3 what is the image of ( p ( - 4,6 ) ) under the composite ( r _ { x - 2 } circ r _ { y - \text { axis } } )?
- ( ( - 8,6 ) ) 2) ( ( 4, - 2 ) ) 3) ( ( 6,0 ) ) 4) ( ( 0,6 ) )
4 find the coordinates of ( r _ { y - \text { axis } } circ r _ { y - pi } ( a ) ) if the coordinates of ( a ) are ( ( 6,1 ) ).
5 find the coordinates of the image of ( ( 2,4 ) ) under the transformation ( r _ { y - \text { axis } } circ t _ { 3, - 5 } ).
6 find the coordinates of point ( n ( - 1,3 ) ) under the composite ( r _ { y - \text { axis } } circ r _ { 90 ^ { circ } } ).
Question 1
Step1: Recall translation composition rule
For translations \( T_{a,b} \) (which translates a point \((x,y)\) to \((x + a,y + b)\)) and \( T_{c,d} \), the composition \( T_{c,d}\circ T_{a,b} \) is equivalent to \( T_{a + c,b + d} \). Here we have \( T_{3,-1} \) followed by \( T_{-5,5} \), so we apply the rule for the composition of translations (note that the order is first \( T_{3,-1} \) then \( T_{-5,5} \), so the composition is \( T_{-5,5}\circ T_{3,-1} \)).
Step2: Calculate the new translation vector
For the \( x \)-component: \( 3+(-5)=3 - 5=-2 \)
For the \( y \)-component: \( -1 + 5 = 4 \)
So the single translation equivalent is \( T_{-2,4} \)
Step1: Recall rotation rules
First, recall the rule for \( R_{180^\circ} \): \( R_{180^\circ}(x,y)=(-x,-y) \)
Then, recall the rule for \( R_{90^\circ} \): \( R_{90^\circ}(x,y)=(-y,x) \)
We need to compute \( (R_{90^\circ}\circ R_{180^\circ})(P) \), which means we first apply \( R_{180^\circ} \) to \( P(2,-3) \), then apply \( R_{90^\circ} \) to the result.
Step2: Apply \( R_{180^\circ} \) to \( P \)
\( R_{180^\circ}(2,-3)=(-2,3) \)
Step3: Apply \( R_{90^\circ} \) to the result
Now apply \( R_{90^\circ} \) to \((-2,3)\). Using \( R_{90^\circ}(x,y)=(-y,x) \), we get \( R_{90^\circ}(-2,3)=(-3,-2) \)? Wait, no, wait: Wait, \( R_{90^\circ}(x,y)=(-y,x) \). So for \((x=-2,y = 3)\), \( -y=-3 \), \( x=-2 \)? Wait, no, I made a mistake. Wait, \( R_{90^\circ} \) is counterclockwise rotation by \( 90^\circ \), the formula is \( (x,y)\to(-y,x) \). So for point \((-2,3)\), \( x=-2 \), \( y = 3 \). Then \( -y=-3 \), \( x=-2 \)? No, wait, no: Wait, let's re - check. The standard \( R_{90^\circ} \) (counterclockwise) is \( (x,y)\to(-y,x) \). So if we have a point \((a,b)\), after \( R_{90^\circ} \) it is \((-b,a)\). So for \((-2,3)\), \( a=-2 \), \( b = 3 \), so \( -b=-3 \), \( a=-2 \)? Wait, that can't be. Wait, no, I think I messed up the order of rotation. Wait, the problem is \( (R_{90^\circ}\circ R_{180^\circ})(P) \), which is \( R_{90^\circ}(R_{180^\circ}(P)) \). So first \( R_{180^\circ}(2,-3)=(-2,3) \). Then \( R_{90^\circ}(-2,3) \): using \( (x,y)\to(-y,x) \), so \( x=-2 \), \( y = 3 \), so \( -y=-3 \), \( x=-2 \)? No, that's wrong. Wait, no, the formula is \( (x,y)\) rotated \( 90^\circ \) counterclockwise is \( (-y,x) \). So for \((-2,3)\), \( x=-2 \), \( y = 3 \), so \( -y=-3 \), \( x=-2 \)? No, that would be \((-3,-2)\)? Wait, no, let's take a simple point. Let's take \((1,0)\), \( R_{90^\circ}(1,0)=(0,1) \)? Wait, no, \( (1,0) \) rotated \( 90^\circ \) counterclockwise is \( (0,1) \)? Wait, no, the correct formula for \( 90^\circ \) counterclockwise rotation is \( (x,y)\to(-y,x) \). So \( (1,0) \): \( -y = 0 \), \( x = 1 \), so \((0,1)\), which is correct. \( (0,1) \) rotated \( 90^\circ \) counterclockwise is \((-1,0)\), using the formula: \( -y=-1 \), \( x = 0 \), so \((-1,0)\), correct. So for \((-2,3)\), \( x=-2 \), \( y = 3 \), so \( -y=-3 \), \( x=-2 \)? Wait, that gives \((-3,-2)\)? But let's check the options. Wait, maybe I mixed up the order of rotation. Wait, the problem is \( (R_{90^\circ}\circ R_{180^\circ})(P) \), which is \( R_{90^\circ}(R_{180^\circ}(P)) \). Wait, maybe I should recall the formula for \( R_{180^\circ} \) is \((x,y)\to(-x,-y)\), so \( R_{180^\circ}(2,-3)=(-2,3) \). Then \( R_{90^\circ}(-2,3) \): using \( (x,y)\to(-y,x) \), so \( -y=-3 \), \( x=-2 \), so \((-3,-2)\)? But let's check the options. Option 4 is \((-3,-2)\). Wait, but let's verify again. Alternatively, maybe the rotation is clockwise? Wait, the notation \( R_{90^\circ} \) usually means counterclockwise, but sometimes clockwise. Wait, the formula for \( 90^\circ \) clockwise rotation is \((x,y)\to(y,-x)\). Let's try that. If \( R_{90^\circ} \) is clockwise, then \( R_{90^\circ}(-2,3)=(3,2) \), which is not in the options. So it must be counterclockwise. So \( R_{90^\circ}(-2,3)=(-3,-2) \), which is option 4.
Step1: Recall reflection rules
First, recall the rule for reflection over the \( y \)-axis: \( r_{y - \text{axis}}(x,y)=(-x,y) \)
Then, recall the rule for reflection over the line \( x = 2 \): \( r_{x = 2}(x,y)=(4 - x,y) \) (since the distance from \( x \) to \( 2 \) is \( |x - 2| \), so the reflected \( x \)-coordinate is \( 2+(2 - x)=4 - x \))
We need to compute \( (r_{x = 2}\circ r_{y - \text{axis}})(P) \), which means we first apply \( r_{y - \text{axis}} \) to \( P(-4,6) \), then apply \( r_{x = 2} \) to the result.
Step2: Apply \( r_{y - \text{axis}} \) to \( P \)
\( r_{y - \text{axis}}(-4,6)=(4,6) \)
Step3: Apply \( r_{x = 2} \) to the result
Now apply \( r_{x = 2} \) to \((4,6)\). Using the formula \( r_{x = 2}(x,y)=(4 - x,y) \), for \( x = 4 \), \( 4-4 = 0 \), so the point is \((0,6)\)
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\( T_{-2,4} \)