Question

What is the image of the point (0, 9) after a rotation 90° clockwise about the origin?

A. (9, 0)

B. (–9, 0)

C. (0, –9)

D. (9, 9)

Answer 1

`\boxed{A'(9,0)}`

Explanation:

When we rotate a point we could rotate it in Clockwise direction because that's how the hand of a clock move, or rotate it in Counterclockwise direction that's the opposite rotation. In math, counterclockwise is defined as being a positive rotation while clockwise is defined as being a negative rotation.

On the coordinate plane, consider the point
`(x,y)`. To rotate this point by 90° around the origin in clockwise direction, you can always swap the x- and y-coordinates and then multiply the new x-coordinate by -1. In a mathematical language this is as follows:

`(x,y)\rightarrow(y,-x)`

So:

`A(0, 9) \rightarrow A'(9,0)`

Finally, the new point is:

`\boxed{A'(9,0)}`