Respostas

2013-08-06T17:54:44-03:00
Como sen 2x = 2 sen x cos x e sen^2 x cos^2 x=1, temos que:

(1/4)^2 + cos^2 x = 1
cos^2 x = 1- 1/16
cos x =  \sqrt{15/16}
cox x = sqtr{15}/4

Daí temos que Sen 2x = 2 * 1/4 * \sqtr{15}/4 = \sqtr{15}/8sqtr{15}/4 \sqrt{15}/4
7 2 7