Math Problem Statement
Triangle PQR is rotated 90 degrees counterclockwise around the origin to form P'Q'R'. The triangle P'Q'R' is reflected across the x-axis to form P''Q''R''.
1
(a)
What are the signs of the coordinates of (x, y) of point P'? (Rotate point P 90 degrees counterclockwise to find your answer.)
A
Both x and y are positive
B
x is negative, y is positive
C
x is positive, y is negative
D
Both x and y are negative
Solution
To determine the signs of the coordinates of point , we need to follow the transformation described:
Step 1: Understand the 90-degree counterclockwise rotation.
When a point is rotated 90 degrees counterclockwise around the origin, its new coordinates are given by: This means:
- The x-coordinate of the new point will be the negative of the y-coordinate of the original point .
- The y-coordinate of the new point will be the x-coordinate of the original point .
Step 2: Analyze the signs of the coordinates after rotation.
Let's consider each quadrant and how the signs change:
- If the original point is in Quadrant I (where both coordinates are positive), after rotation, will be in Quadrant II, where the x-coordinate is negative and the y-coordinate is positive.
- If is in Quadrant II (x is negative, y is positive), after rotation, will be in Quadrant III (both x and y are negative).
- If is in Quadrant III (both x and y are negative), after rotation, will be in Quadrant IV (x is positive, y is negative).
- If is in Quadrant IV (x is positive, y is negative), after rotation, will be in Quadrant I (both x and y are positive).
Since we don’t have the exact coordinates of , the signs of 's coordinates depend on which quadrant is originally located in. But we can conclude from the general rule that a 90-degree counterclockwise rotation changes the signs in this way:
- If is in Quadrant I, then after the rotation, x is negative and y is positive.
Thus, the answer is B: x is negative, y is positive.
Do you need more details or have any questions?
Here are 5 related questions you might consider:
- How does rotating a point by 180 degrees affect its coordinates?
- What are the coordinates of a point after a 270-degree counterclockwise rotation?
- How does reflection across the x-axis change a point's coordinates?
- What are the coordinates of a point after a reflection across the y-axis?
- How would you find the coordinates of after both a 90-degree rotation and reflection?
Tip: Always keep track of the quadrant your point moves to when applying transformations like rotations or reflections to easily determine sign changes.
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Math Problem Analysis
Mathematical Concepts
Geometry
Transformations
Coordinate Geometry
Formulas
(x', y') = (-y, x) for 90-degree counterclockwise rotation
Reflection across x-axis: (x, y) -> (x, -y)
Theorems
Rotation theorem
Reflection theorem
Suitable Grade Level
Grades 8-10