Parameterize a circle based on the contact angle with a wedge

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SUMMARY

The discussion focuses on parameterizing a circular arc based on the contact angle ##\alpha## with a wedge centered at the origin, specifically using the equation $$\left\langle \frac{\sin s}{\sin\alpha},\frac{\cos s - \cos\alpha}{\sin\alpha} \right\rangle : s \in [-\alpha,\alpha]$$. The user seeks to extend this parameterization to account for a wedge defined by the equation ##y=|x|##, with the intention of incorporating a variable wedge angle ##\beta##. The conversation highlights the need for understanding the transformation matrix related to rotations, which is crucial for deriving the desired parameterization.

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  • Understanding of circular arc parameterization
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  • Knowledge of trigonometric functions and their properties
  • Basic concepts of angles in geometry, particularly contact angles
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Hi PF!

Given a 2D plane, the following is a parameterization of a circular arc with contact angle ##\alpha## to the x-axis: $$\left\langle \frac{\sin s}{\sin\alpha},\frac{\cos s - \cos\alpha}{\sin\alpha} \right\rangle : s \in [-\alpha,\alpha]$$

However, I am trying to parameterize a circle based on contact angle ##\alpha## with a wedge centered at the origin; one example of such a wedge might be ##y=|x|## (though I will change the wedge angle ##\beta##, so ideally the parameterization would be a function of both ##\alpha## and ##\beta##).

In this way, we can think of the above parameterization as a limiting value for ##\beta = \pi##.
 
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BvU said:
Hi,

Isn't this a simple rotation over ##\beta## for which the transformation matrix is well known ?
I have no idea how the transformation matrix yields the transformation I listed above. Could you elaborate?

My thought process is, if I know how that was derived perhaps I could derive the specific parameterization I'm seeking.
 

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