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POalgorithm of calculating the slope between line relatively to center coordinate
 

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  1. POalgorithm of calculating the slope between line relatively to center coordinate
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    <p>Please help with the algorithm of calculating the slope So we have a Cartesian coordinate system. X right at Y the top. There is a line which passes through the center of coordinates. Needed to determine the angle relatively to the axis OX.</p> <p>So here's what I'm doing</p> <ol> <li>Certain functions transferred to the origin (top line) and end of line</li> <li>Determine dx, dy</li> <li>Hildren releases two parameters in atan2 (dy, dx)</li> <li>Returns the result in radians.</li> </ol> <p>But! I atan2 works only within 180 degrees. After 180 goes in another direction.</p> <p><strong>So the question: what is the correct algorithm for finding the angle? Do I need to take dy, dx values in magnitude? How to make the arctangent calculated for all 360 and more? I would be glad to hear specific algorithms, or pieces of code comments. Thanx!</strong></p> <pre><code>static inline CGFloat angleBetweenLinesInRadians2 (CGPoint line1Start, CGPoint line1End) { CGFloat dx = 0, dy = 0; dx = line1End.x - line1Start.x; / / whether to do fabs (line1End.x - line1Start.x); dy = line1End.y - line1Start.y; CGFloat rads = atan2 (dy, dx); / / whether to do fabs (rads) return rads; } </code></pre>
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