Math Problem Statement

The curve with equation x = y^2 - 6y + 11 is rotated 90° clockwise about the point P (-2, 3) to give the curve C. What is the equation of curve C?

Solution

The given problem describes a curve with the equation:

x=y26y+11x = y^2 - 6y + 11

This curve is rotated 90° clockwise about a point PP, which has coordinates (2,3)(-2, 3), to obtain a new curve CC. The task is to find the equation of the new curve CC.

Step 1: Equation of the Original Curve

The original curve is: x=y26y+11x = y^2 - 6y + 11 This can also be written in the form f(y)f(y), meaning it relates xx as a function of yy.

Step 2: Shift the Coordinates to the Origin

Since we are rotating around the point P(2,3)P(-2, 3), we first need to shift the coordinates so that PP becomes the origin. To do this, we perform the following translation:

  • Let x=x+2x' = x + 2
  • Let y=y3y' = y - 3

Thus, the original curve becomes: x2=(y+3)26(y+3)+11x' - 2 = (y' + 3)^2 - 6(y' + 3) + 11 Simplifying the right-hand side:

(x2)=(y2+6y+9)6(y+3)+11(x' - 2) = (y'^2 + 6y' + 9) - 6(y' + 3) + 11 x2=y2+6y+96y18+11x' - 2 = y'^2 + 6y' + 9 - 6y' - 18 + 11 x2=y2+2x' - 2 = y'^2 + 2 x=y2+4x' = y'^2 + 4

So the equation in the shifted coordinates is: x=y2+4x' = y'^2 + 4

Step 3: Rotate the Curve 90° Clockwise

To rotate the curve 90° clockwise around the origin, we apply the following transformation: x=yx'' = y' y=xy'' = -x'

Thus, the new curve in the rotated coordinates is: y=(y2+4)y'' = -(y'^2 + 4) or equivalently: y=y24y'' = -y'^2 - 4

Step 4: Shift Back to the Original Coordinates

Now, we reverse the shift to return to the original coordinates xx and yy: x=x+2x = x'' + 2 y=y+3y = y'' + 3

Substitute y=y24y'' = -y'^2 - 4 into the second equation: y=y24+3y = -y'^2 - 4 + 3 y=y21y = -y'^2 - 1

Thus, the final equation of the new curve CC is: y=(x2)21y = -(x - 2)^2 - 1

This is the equation of the curve CC after a 90° clockwise rotation about the point P(2,3)P(-2, 3).

Would you like further clarification or details?


Here are 5 related questions for practice:

  1. How would the equation change if the rotation was 90° counterclockwise?
  2. What is the general transformation matrix for rotating a point around an arbitrary point?
  3. How would you solve for the new equation if the curve was translated instead of rotated?
  4. What are the key differences in the equations of curves when rotating by different angles (e.g., 180°, 270°)?
  5. How do you find the points of intersection between two rotated curves?

Tip: Always break down rotations into translations to the origin and apply coordinate transformations step by step to avoid mistakes.

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Math Problem Analysis

Mathematical Concepts

Coordinate Geometry
Rotations
Algebraic Manipulation
Translation of Coordinates

Formulas

x' = x + a, y' = y + b (Translation of Coordinates)
x'' = y', y'' = -x' (90° Clockwise Rotation)
Equation of a quadratic curve

Theorems

Transformation of Coordinates
Rotations in the Coordinate Plane

Suitable Grade Level

Grades 10-12