Question

Sendo x= 90º
Y= cos4x+sin2x+tg2x-sec4x

Answer 1

cos 4x = cos 4 . 90 = cos 360 = 1
sen 2x = sen 2 . 90 = sen 180 = 0
tg 2x = tg 180 = 0
sec 4x = sec 360 (como sec x= 1/cosx)
sec 360 = 1/cos 360 = 1/1 = 1
Y = 1 + 0 + 0 - 1 = 0