$(a)\;(\frac{3+ \sqrt{3}}{4})+(\frac{3- \sqrt{3}}{4})i\qquad(b)\;(\frac{5+ \sqrt{3}}{4})+(\frac{5- \sqrt{3}}{4})i\qquad(c)\;(\frac{3+ \sqrt{5}}{4})+(\frac{3- \sqrt{5}}{4})i\qquad(d)\;(\frac{7+ \sqrt{3}}{4})+(\frac{7- \sqrt{3}}{4})i$