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In the given figure, O and O' are centers of two circles, AB // CD // OO', then which of the following is not true :

In the given figure, O and O' are centers of two circles, AB // CD // OO', then which of the following is not true : Circle, Concise Mathematics Solutions ICSE Class 9.
  1. AB = 2 × OO'

  2. CD = 2 × OO'

  3. AB = CD

  4. AB ≠ CD

Circles

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Answer

Draw ON and O'M perpendicular to AB.

In the given figure, O and O' are centers of two circles, AB // CD // OO', then which of the following is not true : Circle, Concise Mathematics Solutions ICSE Class 9.

We know that,

Perpendicular from center to the chord bisects it.

∴ AN = NP and MP = MB

From figure,

⇒ AB = AN + PN + MP + MB

⇒ AB = PN + PN + MP + MP

⇒ AB = 2PN + 2MP

⇒ AB = 2(PN + MP)

⇒ AB = 2NM

⇒ AB = 2OO' …………(1)

Draw OE and O'F perpendicular to CD.

We know that,

Perpendicular from center to the chord bisects it.

∴ CE = EQ and QF = FD

From figure,

⇒ CD = CE + EQ + QF + FD

⇒ CD = EQ + EQ + QF + QF

⇒ CD = 2EQ + 2QF

⇒ CD = 2(EQ + QF)

⇒ CD = 2EF

⇒ CD = 2OO' …………(2)

From equation (1) and (2), we get :

⇒ AB = CD.

Hence, Option 4 is the correct option.

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