Question

Se senx =5/13, cosx = 12/13 e tgx = 5/12, então o valor de sen 2x é:

Answer 1

sen 2x = 2 (senx·cosx)
sen 2x = 2 (5/13)·(12/13)
sen 2x = 2 (60/169)
sen 2x = 120/169

Answer 2

$Sen ~2x=sen( x+x)=sen~x.cos~x ~+~sen~x.cos~x=2sen~x~cos~x=$$2. \frac{5}{13} . \frac{12}{13} = \frac{120}{169}$