They are reflections of each other across the line [math]y=x[/math]. Why?[br]This line has an angle of [math]45^\circ[/math], and you can notice that both [math]90^\circ-\theta[/math] and [math]\theta[/math] are the same rotation from this angle, but in opposite directions. [br][math](90^\circ-\theta)-45^\circ=45^\circ-\theta[/math][br][math]\theta-45^{\circ}[/math][br]Since these are negations, they represent the same size rotation, but in opposite directions.

Reflecting across [math]y=x[/math] takes [math]P=\left(\cos\theta,\sin\theta\right)[/math] to the point [math]P'=\left(\sin\theta,\cos\theta\right)[/math]

[math]\left(\cos\left(90^\circ-\theta\right),\sin\left(90^\circ-\theta\right)\right)[/math]