срочнооо пожалуйста ​

(sint - cost)² = 1 - sin2t

sin²t - 2sintcost + cos²t = 1 - sin2t

1 - sin2t = 1 - sin2t

⬛

cos⁴t - sin⁴t = (cos²t - sin²t) (cos²t+sin²t) = cos 2t * 1 = cos 2t

cos 2t = cos 2t