Given: z=2−i(2tan85π)
⇒z=2[1−itan(85π)]
⇒z=2[1−cos(85π)isin(85π)]
⇒z=cos(85π)2[cos(85π)−isin(85π)]
⇒z=cos(π−83π)2[cos(π−83π)−isin(π−83π)]
⇒z=−cos(83π)2[−cos(83π)−isin(83π)]
⇒z=cos(83π)2[cos(83π)+isin(83π)]
⇒z=2sec83πei⋅83π
Now on comparing with z=∣z∣eiθ we get,
⇒θ=83π,r=2sec83π