Sin(13x + π/4) ≤ √2
2
-π - π + 2πn α ≤ 13x +π/4 ≤ π + 2πn, n∈Z
4 4
- 5π + 2πn ≤ 13x + π/4 ≤ π + 2πn
4 4
-5π - π + 2πn ≤ 13x ≤ π - π + 2πn
4 4 4 4
- 6π + 2πn ≤ 13x ≤ 2πn
4
- 3π + 2πn ≤ 13x ≤ 2πn
2
-3π +4πn ≤ x ≤ 2πn
2*13 13
π (4n -3) ≤ x ≤ 2πn
26 13
x∈ [ π(4n-3); 2πn ], n∈Z
26 13