Question 484942
<pre>
A negative angle like -90° is a clockwise rotation of 90° from the 
right side of x-axis downward to the y-axis indicated by this curved 
arrow:

{{{drawing(300,300,-.9,.9,-.9,.9, graph(300,300,-.9,.9,-.9,.9),
green(line(0,0,0,-.7)), locate(.14,-.14,"-90°"),
arc(0,0,.4,-.4,270,360),line(.05,-.17,0,-.2),line(.05,-.215,0,-.2)  )}}}

It is between quadrants III and IV.  It is not in any quadrant.

It's referent angle is 90° because that is the smallest positive angle
between the green line and the x-axis.

Edwin</pre>