Question

sabendo que sen 20°=a, obtenha sen 160°,sen 200° e sen 340° em funçao de a.

Answer 1

A) Sen 160 = sen (180 - 20) ->
Sen 180.Cos20-sen20.Cos 180 =
0. Cos20 - a. -1 = a

B) sen 200 = sen (180+20)
Sen 180.cos20 + sen20.cos180 -> 0. Cos20 + a. -1 = -a

C) sen 340 = sen (360-20)
Sen360.cos20-sen20.cos360 ->
0.cos20-a.1 = -a