Rotate Point p: How to Rotate by 75° Counterclockwise

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Discussion Overview

The discussion revolves around the problem of rotating a point, specifically point p=(3,3√3), counterclockwise about the origin by 75 degrees. Participants explore various methods for determining the new coordinates after the rotation, including mathematical approaches and visual strategies.

Discussion Character

  • Exploratory
  • Mathematical reasoning
  • Conceptual clarification

Main Points Raised

  • One participant expresses uncertainty about how to rotate a point and seeks guidance on the process.
  • Another participant suggests using a rotation matrix to represent the counterclockwise rotation, providing the matrix form for rotation by an angle θ.
  • A different approach is proposed that involves calculating the distance from the origin to the point and determining the angle of inclination, followed by adjusting this angle by adding 75 degrees to find the new coordinates.
  • One participant recommends a visual approach, suggesting that drawing a picture of the point and its rotated position may help understand the rotation without relying on formulas.

Areas of Agreement / Disagreement

Participants present multiple approaches to solving the problem, indicating that there is no consensus on a single method. The discussion includes both mathematical and visual strategies, reflecting a range of perspectives on how to tackle the rotation.

Contextual Notes

Some methods rely on specific mathematical assumptions, such as the use of trigonometric functions and the properties of rotation matrices. The effectiveness of visual strategies may depend on individual interpretation and drawing accuracy.

GloriousGoats
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My problem reads as follows: Point p=(3,3√3) is rotated counterclockwise about the origin by 75 degrees. What are the coordinates after this rotation?
I have no idea how to rotate a point, let alone by 75 degrees.
 
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Hint 1: The matrix
$$\begin{pmatrix}\cos\theta & -\sin\theta \\ \sin\theta & \cos\theta\end{pmatrix}$$
represents a counterclockwise rotation of $\theta$ about the origin.

Hint 2: $75^\circ\ =\ 45^\circ+30^\circ$.
 
Last edited:
The way I would approach this is:

1.) Find the distance \(r\) from the origin to the given point, and find the angle of inclination \(\theta=\arctan(m)\), where \(m\) is the slope of the line through the origin and the given point. Let \(\alpha=\theta+75^{\circ}\).

2.) The rotated point will then be:

$$(r\cos(\alpha),r\sin(\alpha))$$
 
GloriousGoats said:
My problem reads as follows: Point p=(3,3√3) is rotated counterclockwise about the origin by 75 degrees. What are the coordinates after this rotation?
I have no idea how to rotate a point, let alone by 75 degrees.

If you think about where the point p is and where it will be after the rotation, you won't need any rotation formulas or addition formulas, just the basic angles. Draw a picture.
 

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