If two straight lines are perpendicular to the same line, prove that they are parallel to each other.
AB⊥PQ,
Therefore, ∠ABD = 90° _____________ (i)
CD⊥PQ,
Therefore, ∠CDQ = 90° _____________ (ii)
From equations (i0 and (ii)
∠ABD = ∠CDQ = 90°
Hence, AB||CD because Cross ponding angles are equal.
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