Question 1157259
2(1-sin^2 t)-sin t=-1
2-2sin^2 t-sin t=-1
0=2sin^2t+sin^t-3
0=(2 sin t+3)(sin t -1)
sin t=1, and that occurs when theta=90 deg or pi/2 rad.
cos t=0 at pi/2
2 cos^2  pi/2-sin pi/2=0-1=-1