let z=cos(theta)+i.sin(theta)/(cos theta – i.sin theta),

theta lies between pi/2 to pi/4. Then arg z is

1. 2theta
2. 2theta – pi
3. pi + 2theta
4. none of these

Dear Student,
Rationalize Z and on simplification you will get,

z = cos (2theta) + i sin (2theta)
Now, arg z = tan-1 (tan (2theta)),
Since theta varies from pi/4 to pi/2.
Therefore 2theta varies from pi/2to pi.
Therfore , arg z = 2theta – pi Answer.