ctg²t (1-cos2t)+cos²t
Используем формулы: 1=cos²t+sin²t cos2t=cos²t-sin²t ctgt=cost/sint Упростим ctg²t(cos²t+sin²t-(cos²t-sin²t))+cos²t=ctg²t(cos²t+sin²t-cos²t+sin²t)+cos²t= cos²t/sin²t * 2sin²t+cos²t=2cos²t+cos²t=3cos²t