Question

Sendo sen x =
5
3
e 0 < x < 2 π , calcule o valor do cos 2x

Answer 1

senx = 3/5 => sen²x = 9/25
Cos²x = 1 -sen²x = 1 -9/25 = 16/25

Cos 2x = Cos²x - sen²x
Cos 2x = 16/25 - 9/25
Cos 2x = 7/25 ✓