Math Problem Statement

Fungsi linear y = x + 7 dirotasikan searah jarum jam sebesar 90 derajat terhadap titik pusat. Bayangan dari fungsi linear tersebut adalah...

Solution

The given problem asks for the transformation of the linear function y=x+7y = x + 7 when it is rotated clockwise by 9090^\circ about the origin.

Step-by-step solution:

  1. Original Line Equation: The line equation is y=x+7y = x + 7. In slope-intercept form, the slope mm of this line is 1 (since y=mx+cy = mx + c, where m=1m = 1 and c=7c = 7).

  2. Clockwise Rotation by 9090^\circ:

    • When a line with slope mm is rotated by 9090^\circ clockwise about the origin, its new slope becomes the negative reciprocal of mm, i.e., mnew=1mm_{\text{new}} = -\frac{1}{m}.
    • In this case, since m=1m = 1, the new slope after a 9090^\circ clockwise rotation will be mnew=1m_{\text{new}} = -1.
  3. New Line Equation:

    • The new equation of the line will have the form y=x+cy = -x + c. To find cc, the line must pass through the same point on the original line that was rotated.
    • The line intersects the y-axis at (0,7)(0, 7). After rotating this point 9090^\circ clockwise, the new coordinates of the point are (7,0)(7, 0).
  4. Final Equation:

    • Using the point (7,0)(7, 0), substitute it into the new equation y=x+cy = -x + c: 0=7+c    c=70 = -7 + c \implies c = 7
    • Thus, the new equation of the line is y=x+7y = -x + 7.

Conclusion:

The equation of the line after a 9090^\circ clockwise rotation is y=x+7y = -x + 7.


Would you like more details or have any questions?

Here are five related questions to explore further:

  1. What happens when the line is rotated 9090^\circ counterclockwise instead?
  2. How do you rotate a line around a different point other than the origin?
  3. What is the geometric meaning of rotating a line about the origin?
  4. How would the transformation change if the rotation angle were 180180^\circ?
  5. Can you rotate other types of curves, like parabolas, in the same way?

Tip: Rotating lines involves changing their slope, but always remember that rotations around the origin also involve changing the coordinates of points on the line!

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Math Problem Analysis

Mathematical Concepts

Linear Equations
Rotation
Coordinate Geometry

Formulas

y = mx + c
Rotation transformation

Theorems

Rotation by 90 degrees around the origin

Suitable Grade Level

Grades 9-10