given intergrate from 0 to 2pi

(sin t)^2 dz / jz

---------

5- 4 cos t

i achieve the C_-1 equation till

( z^2 + z^-2 - 2) ( -j )

----------------------- dz

-20z + 8z^2 + 8

The pole are 2 & 0.5. ( Only 0.5 is lying in |z|=1 )

But i can't get the final answer which is ( pi/4) when i sub z =0.5 into

( z^2 + z^-2 - 2) * (2pi)

------------------

-----20+16z

many thanks

ck