... = 18 0 ( 60 ) + k 360 , k  x = 400 + k1800 , k  0 x = 11 0 + k180 , k  Bi 3c sgk/28 3x cos ữ = 3x cos ữ = cos ữ x = + k , k  x = + k , k  x 11 = 12 ... -f(x) Nờn hm f khụng chn cng khụng l Bi 1. 2 /12 - SBT a y = cosx +1 GV: K? HS: cosx +1 Bi 1. 2 /12 - SBT Tỡm xỏc nh cỏc hm s sau: a y = cosx +1 k: cosx +1 cosx -1 Tha x R cos x sin x GV: Theo cụng ... , k  x = + k , k  12 11 x = 18 + k , k  x = + k , k  18 Bi 5b sgk/28 cot ( x 1) = cot ( x 1) = cot ữ 5 k 3x = + k , k  x = + + ,k  18 Bi sgk/28 - Ta cn tỡm nhng...