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How do I answer this question?Use the coordinate rules to rotate triangle ABC 90...

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it-sall-in-th... | eNoter

Posted May 13, 2013 at 11:31 AM via web

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How do I answer this question?
Use the coordinate rules to rotate triangle ABC 90 degrees counterclockwise around the origin. List the coordinates and draw the image of triangle A'B'C'. (a,b)translates to(______,_____)
A(-1,-2)translates to A'(____,____)
B(1,2) translates to B'(______,____)
C(3,-1) translates to C'(______,____)

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Tagged with geometry, math, rotations

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pramodpandey | College Teacher | Valedictorian

Posted May 13, 2013 at 12:08 PM (Answer #1)

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Let coordinate of A'(x',y') ,A(-1,-2)=A(x,y)

we know

x'=xcos(theta)-ysin(theta)

y'=xsin(theta)+y cos(theta)

Thus

x'=(-1)cos(90)-(-2)sin(90)

x'=2

y'=-1sin(90)=-1   ,

A'(x',y')=A'(2,-1)

B(x,y)=B(1,2)

B'(x',y')=?

x'=1 cos(90)-2sin(90)=-2

y'=1sin(90)+2cos(90)=1

B'(x',y')=B'(-2,1)

C(x,y)=C(3,-1)

C(x',y')=?

x'=3cos(90)-1sin(90)=-1

y'=3sin(90)+1cos(90)=3

C(x',y')=C(-1,3)

A(-1,-2)translates to A'(2,-1)
B(1,2) translates to B'(-2,1)
C(3,-1) translates to C'(-1,3)

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