cos?=?3?/2for?=5?/6,7?/6socos2x=?3?/2 for2x=5?/6,7?/6. In other words,x=5?/12,7?/12 Additional solutions are found by adding2?n/2=?n. Thus, four solutions in the interval[0,2pi]are5?/12,7?/12,17?/12,19?/12 Solution cos?=?3?/2for?=5?/6,7?/6socos2x=?3?/2 for2x=5?/6,7?/6. In other words,x=5?/12,7?/12 Additional solutions are found by adding2?n/2=?n. Thus, four solutions in the interval[0,2pi]are5?/12,7?/12,17?/12,19?/12.