inverse of tan at 90 degree

Hi.

Iam using "atand((y2-y1)/(x2-x1))" function to calculate angle. But i incure problem when my denomitor is zero. Sometimes it gives +90 and sometimes -90 degree, even though sign of cordinates of every point is same.

Please suggest way to resolve this issue.

[James Tursa]

Please give specific example, with numbers, to show where you are getting +90 and -90 even though you think the signs of the inputs are the same.

Answer 1

[Star Strider]

A more robust approach would be atan2d, since it provides a 4-quadrant angle.

y2 = 20;
y1 = 10;

x2 = 42;
x1 = 42;

Theta1 = atan2d((y2-y1), (x2-x1))

Theta1 = 90

y2 = 10;
y1 = 20;

x2 = 42;
x1 = 42;

Theta2 = atan2d((y2-y1), (x2-x1))

Theta2 = -90

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