[11} points} 6. Let n be an positive integer. Compute cosfnm) cos(5:c}d:c. -d|.' (Remark: This is a special case of a general formula we have learned. Just applying that formula is not 0k. You must do the computation by yourself and write down the detail.) (Hint: cosacos = $003M + ,8) + $60301 m.)