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May 16th, 2017, 12:42 PM  #1 
Newbie Joined: May 2017 From: Croatia Posts: 2 Thanks: 0  A question about converting cylindrical coordinates to rectangular coordinates
I have a problem figuring something out when it comes to converting cylindrical to 3D rectangular coordinates. the formulas for converting are as follows: x = r cos theta y = r sin theta z = z If we're just using basic trigonometry to figure out the sides of the triangle of which the angle theta is a part of, and the angle itself lies between x and r, how can we use any of these functions to figure out the y if y is not a part of the same triangle with x and r? Shouldn't the angle between r and y be something other than theta ? How can we get y by applying these functions to theta then? Can anyone please explain this? Thanks. Last edited by skipjack; May 17th, 2017 at 06:17 AM. 
May 19th, 2017, 03:28 AM  #2 
Math Team Joined: Jan 2015 From: Alabama Posts: 2,575 Thanks: 667 
I don't understand how it could possibly happen that "y is not a part of the same triangle with x and r". "r" is, by definition of "polar" (and so "cylindrical") coordinates, the line from the origin to the point (x, y). It is always the hypotenuse of a right triangle having x and y as legs.


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converting, coordinates, cylindrical, question, rectangular 
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