To rotate a point by 90 degrees counterclockwise about the origin, you can use the following transformation:

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

This formula will give you the new coordinates after a 90-degree rotation. Now let's apply this transformation to the points given:

1. For $C(3, -2)$: $C' = (-(-2), 3) = (2, 3)$

2. For $D(5, 2)$: $D' = (-(2), 5) = (-2, 5)$

3. For $E(7, 0)$: $E' = (-(0), 7) = (0, 7)$

So, the rotated coordinates are:

• $C'(2, 3)$
• $D'(-2, 5)$
• $E'(0, 7)$

Let me know if you'd like more details or have any questions!

Here are 5 related questions for further understanding:

1. How would the coordinates change if the rotation were 180 degrees instead of 90 degrees?
2. What happens if we rotate the triangle 90 degrees clockwise instead of counterclockwise?
3. How can you apply a 270-degree counterclockwise rotation to these points?
4. What is the general rule for rotating any point about the origin by 90 degrees?
5. How can you verify that the points have been rotated correctly?

Tip: To visualize rotations, try sketching the original and rotated points on graph paper to see the transformation clearly.