= 1-2sin^2 18 - sin18 <span> = 1-2[(1/4)(sqrt5 - 1)]^2 - (1/4)(sqrt5 - 1), since sin18 = (1/4)(sqrt5 - 1) </span> <span> = 1 - (1/8)(6-2sqrt5) - (1/4)(sqrt5 - 1) </span> <span> = 1 - 3/4 + 1/4 </span> <span> = 2/4 </span> <span> = 1/2 </span> I hope my answer has come to your help. Thank you for posting your question here in Brainly. We hope to answer more of your questions and inquiries soon. Have a nice day ahead!
