If sin (x + y) = cos {3 (x + y)}, then the value of tan {2(x + y)} is
1
0
A.
1
sin (x + y) = cos {(3 (x + y)}
cos {90° - (x + y) = cos {3(x + y)}
90° - (x + y) = 3(x + y)
4 (x + y) = 90°
2 (x + y) = 45°
∴ tan [2(x + y)} = tan 45° = 1
If x sin3θ + y cos3θ = sin θ cos θ ≠ 0
and x sin θ - y cos θ = 0, then the value of (x2 + y2) is
sin θ - cos θ
sin θ + cos θ
0
1