Question

The pre-image of triangle ABC is rotated 90 degrees to image A’B’C’ about the origin. If point B is located at (-1,4), then name the coordinates of B’.

Answer 1

If you rotate a point (A,B) 90 degrees about the origin the new coordinate will be (-B, A)

Answer 2

so (-4, -1)

Answer 3

Yes.

Answer 4

but that is not one of the choices

Answer 5

choices are (1, 2) (4, 1) (-2, 1) (-1, -2)

Answer 6

Are you sure you copied the problem correctly? Is there a picture of the original problem with answers that you can post?

Answer 7

one minute

Answer 8

did you see it?

Answer 9

Yeah, I saw the question but there was no diagram.
I am thinking now the triangle is rotated clockwise instead of anticlockwise.
The formula I gave you was for positive 90 degree rotation (meaning anticlockwise).

Answer 10

yes there is not diagram

Answer 11

so would it be (4, 1) ?

Answer 12

Yes. Rather than remembering too many formulas, just remember one thing.

(A,B) rotated 90 degrees will change to (-B, A).
That is switch the x and y coordinates and change the sign on x.
Rotate it again 90 degrees it becomes (-A, -B)
Rotate it again 90 degrees it becomes (B, -A) (This is 270 degrees rotation which is the same as rotating 90 degrees clockwise)

So (-1, 4) will become (4, 1) when rotated 90 degrees clockwise.

Answer 13

ok. thanks!

Answer 14

you are welcome.