The terminal side is in the fourth quadrant,
In fourth quadrant the cosine value are greater than or equal to zero,
When we rotate the angle by pi/2, the terminal side will be in first quadrant,
where in first quadrant all the values are positive,
so the value of cosine cannot be negative
Option B. -X is not possible,
Thus, 2X, X/2, X can be possible
the value of Cosine is X
and the value of Cos(T+90)=CosTCos90-SinTSin90
Cos(T+90)=X(0)-cos(90-T)1
Cos(T+90)=0-(-X)1
Cos(T+90)=X
ANSWER :
D. X
