How to rotate a fixed length Line about a perimeter of a circle

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S 2020-9-14

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https://ww2.mathworks.cn/matlabcentral/answers/593254-how-to-rotate-a-fixed-length-line-about-a-perimeter-of-a-circle

评论： S 2020-9-15

I am new to coding matlab.

I wish to code the above situation as shown in to picture where a fixed length line(or tangent) is rotated inside a large grid in a circular manner with fixed radius and the center is chosen same as the large grid.

Any suggestion - how can I proceed to code above situation ?

Thank you.

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Matt J 2020-9-14

What would be the input and output of such code?

S 2020-9-15

I am trying to learn how to use the rotation matrix formula for different situations.

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Answer 1

Image Analyst 2020-9-14

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https://ww2.mathworks.cn/matlabcentral/answers/593254-how-to-rotate-a-fixed-length-line-about-a-perimeter-of-a-circle#answer_494317

It's simple geometry. Just pick a radius, then go from 0 to 2*pi, or whatever angles you want. The slope is

angle = linspace(0, 2*pi, 360);
y = radius * sind(angle);
x = radius * cosd(angle);
slope = atand(y/x);

The slope of the perpendicular to that point is -1/slope. Now pick a new radius that is the length of the little line segment you want to create and create new x,y values (xr, yr) using the above formulas. These will be relative to the origin. Then add the original x,y to move that line segment from the origin to the (x,y) point out at the circle perimeter. It sounds like homework so that's why I'm not providing a full solution but it's pretty easy now that I've explained it and you'll have no problem finishing it.