What is the purpose of the arrowhead in angle arc?
What is the purpose of the arrowhead in the arcs of angles? Specifically, please see the two plot-images I've uploaded. What is the difference of placing the arrowhead in the beginning or at the end of the arc?
Ok, lets ignore the blue angle and arc. I am interested in the red only. What difference does it make if the arrowhead is on the $0$ degrees ray or on the $30$ degrees ray?
Also, does the arc necessary imply that the angle is changing or can an arc be used for a static angle that does not change ?
$\endgroup$ 11 Answer
$\begingroup$An angle is between two half lines. You need to indicate which is the origin and which is the destination, to avoid a sign ambiguity.
In the context of complex arguments, you may consider that the origin is implicitly the $x$ axis.
Your second figure is wrong. $\phi$ being a negative angle, $\phi-90°$ must extend past the negative $y$ axis.
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