MHB Rotate Point p: How to Rotate by 75° Counterclockwise

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The discussion focuses on rotating the point p=(3, 3√3) counterclockwise about the origin by 75 degrees using matrix rotation. The rotation matrix provided is $$\begin{pmatrix}\cos\theta & -\sin\theta \\ \sin\theta & \cos\theta\end{pmatrix}$$, which applies to any angle θ. The approach involves calculating the distance from the origin and the angle of inclination, followed by determining the new coordinates using the formula $$(r\cos(\alpha), r\sin(\alpha))$$ where α is the sum of the original angle and 75 degrees.

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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: $75^\circ\ =\ 45^\circ+30^\circ$.
 
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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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