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this i an interview question i encountered with HULU.
Given two circles, one has radius 1 and the other has radius 2. Let the small one rotate along the perimeter of the big one. how many circles will the small one rotates when it has moves one round inside the big one? and what about outside?
The perimeter of the circle of radius 1 is 2*PI*1 and the other one is 2*PI*2.
Then when the little circles rotates inside it makes 2 round and same thing at the outside... Maybe I don't understand anything...
how many diameters of the small circle are in one diameter of the big one?
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I have bumped into the following statement in an Engineering journal. The statement is mentioned on right side example.
A 640x480 image with a horizontal FOV of 47 degrees gives focal length
f = 740 pixels.
Please let me know the calculations behind this as I am very new to Computer vision.
AFAIU 740 is not the exact answer for such data but close enough. According to my understanding
f = (width/2) * ctg(HFOV/2)
which give me f = 735.95. And to reverse for f = 740 the HFOV should be 46.77°.
The math behind is following: assume that on their Figure 2 Y1 is actually the top point on the sensor (I'll use vertical field of view here instead of horizontal because it allows me to use that image). Now consider the triangle O-P-Y1. In that triangle ∠P is half of the FOV. On the other hand ctg(∠P) = ctg(FOV/2) is OP/OY1 which is f/(height/2).
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I have searched a lot of google, reviewed my old mathematics books, But I am stuck why can't we find area of an irregular shape from its perimeter? If we have find perimeter from area, Is that possible to reverse the process and find area from perimeter.
This process is working fine for square and rectangle but not for totally irregular shapes.
I'm asking this question because we have one field with irregular shape, and we want to know its area, We can measure its 5 sides.
Don't we have any method to find area from perimeter for irregular shapes.
Any help will be appreciated.
Consider a rope and form an irregular shape. Measure it's area. Now change the shape you just formed with the rope. Measure the area again. Is it the same? Not necessarily.
Or consider a square and a rhomb (which is not a square) with the same perimeter. Do they have the same area? No. Therefore, how do you think could you find out what its area is if you don't have the information of the shape?
You cannot get the area if you just have the information of the perimeter, but don't know anything else.
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I am trying to work out some circle detection and I'm having trouble working out some angles, can anyone tell me how to get the angle value of these blue angles.
I have never worked with angles before, so can someone point me to some relevant functions, algorithms etc.
The external angles of a polygon sum to 360 degrees, so if you have a regular polygon with N vertices then each external angle would be 360 / N.
In your example above N = 8, so assuming the points are equally spaced, the external angles are each 360 / 8 = 45 degrees.
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Here you can see a representation of the problem I need to solve
http://imageshack.us/photo/my-images/542/002yw.png http://imageshack.us/photo/my-images/542/002yw.png
I've two circles defined by their positions BS1 and BS2.
Now I need to get the position of the point A and the only data I've is the distance from point BS1 that is defined by its radius.
Can someone please tell me how can I find the coordiinates of point A?
Thank you very much
PD: I need to do the same with point B.
For simplicity lets say, on your left side of the image you have a center c1, radius r1, and point A. On the right side center c2, radius r2 and point B..
A = ((s1-s2)/|s1-s2|)*r1 + s1
B = ((s2-s1)/|s1-s2|)*r2 + s2
Do not forget, this are vectors.. If you can not understand this equation, tell me and Ill explain it to you.
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I want to draw a 3d line from one 3d point to another 3d point.
I know the source point, but need to calculate the destination point. I have the angle and the length of the line. The y coordinate (the height) is the same for the source and the destination point.
Thanks
Basic trig, imagine a bunch of triangles along the various planes and solve for the sides/angles you want to know.
If you give us some sample values for what you already know we can show you the maths.