Прямые \(a\) и \(b\) параллельны, если:
1) \(\angle3 + \angle5 = 180^\circ\)
2) \(\angle2 + \angle6 = 180^\circ\)
3) \(\angle3 + \angle6 = 180^\circ\)
4) \(\angle1 = \angle4\)
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