Mathematics

AB and CD are two equal chords of a circle with center O which intersect each other at right angle at point P. If OM ⊥ AB and ON ⊥ CD; show that OMPN is a square.

Circles

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Answer

AB and CD are two equal chords of a circle with center O which intersect each other at right angle at point P. If OM ⊥ AB and ON ⊥ CD; show that OMPN is a square. Circle, Concise Mathematics Solutions ICSE Class 9.

Since, OM ⊥ AB and ON ⊥ CD.

∴ ∠OMP = ∠ONP = 90°.

Given,

AB and CD intersect at right angle.

∴ ∠MPN = 90°.

We know that,

Sum of angles of quadrilateral equal to 360°.

∴ ∠OMP + ∠ONP + ∠MPN + ∠MON = 360°

⇒ 90° + 90° + 90° + ∠MON = 360°

⇒ 270° + ∠MON = 360°

⇒ ∠MON = 360° - 270° = 90°.

Given,

AB = CD

We know that,

Equal chords are equidistant from the center.

∴ OM = ON = x (let) …………(1)

Since,

⇒ AB ⊥ CD and ON ⊥ CD

∴ AB || ON

∴ MP || ON.

⇒ OM ⊥ AB and CD ⊥ AB

∴ OM || CD

∴ OM || PN.

Since, in quadrilateral OMPN opposite sides are parallel.

∴ OMPN is parallelogram.

We know that,

Opposite sides of parallelogram are equal.

∴ MP = ON = x and OM = PN = x

∴ MP = ON = OM = PN.

Since, all sides of quadrilateral OMPN are equal and each interior angle to 90°.

Hence, proved that OMPN is a square.

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