2sin3π5cos3π5+i.2cos23π5 2cos3π5[sin3π5+icos3π5] But r=2cos3π5=−ive Hence are rewrite as under: z=−2cos3π5[−sin3π5−icos3π5] =−2cos3π5[cos(3π2−3π5)+isin(3π2−3π5)] =−2cos3π5[cos9π10+isin9π10] r=−2cos3π5(+ive) and θ=9π10 and which lives between −π and π