Question

Cos x - sen x = 3/4
Quanto vale sen 2x

Answer 1

Cos x - sen x = 3/4

(Cos x - sen x)² = (3/4)²

(cos²x+sen²x) - [2.senx.cosx] = 9/16

(1) - [sen 2x] = 9/16

sen 2x = 1 -9/16

sen 2x = 7/16 ✓