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I want to rotate a line so that it lies on the positive x direction. I can determine the equation of the line as y=m*x+c where m is the slope and c is the intercept. The angle of rotation, theta is known by tan inverse of m. Now theta can be either -theta or -(pi+theta) depending on the quadrant in which the line lies.

How can I know which of these thetas i should use directly by looking at the equation of the line. I need to rotate about 400 lines so manually looking at each line can be time intensive. I can use an if else loop in my code to do it automatically.

Thanks.

Nancy

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# Calculating angle of a rotation for a line

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