we have that
step 1
convert to degrees
∅=9pi/2--------> convert to degrees----> 9*180/2----> 810°
810°/360°----> 2.25
0.25*360------> 90°
∅=90°---------> belong to the I quadrant
step 2
find the x-y coordinates in the unit circle
r=1 unit
x=r*cos ∅------> 1*cos 90------> x=0
y=r*sin ∅------> 1*sin 90°------> y=1
the answer is
the point is (0,1)
