**Akki chauhan**

The concentric circle are the circles with a common center the region between two concentric circle of different radii is called an annulus.

*-Answered by Akki chauhan* On 15 January 2019:09:05:48 AM

**Question 1.** **Asked on :**13 January 2019:11:15:32 AM

Define concentric circles.

*-Added by Akki chauhan* **Mathematics** » **Circles**

**Answer:**

The concentric circle are the circles with a common center the region between two concentric circle of different radii is called an annulus.

*-Answered by Akki chauhan* On 15 January 2019:09:05:48 AM

**Question 2.** **Asked on :**12 January 2019:05:52:26 PM

prove that the cyclic parallelogram is rectangle.

*-Added by khushi chauhan* **Mathematics** » **Circles**

**Answer:**

∠A + ∠C = 180 ....1

But ∠A = ∠C

So ∠A = ∠C = 90

Again

∠B + ∠D = 180 ....2

But ∠B = ∠D

So ∠B = ∠D = 90

Now each angle of parallelogram ABCD is 90.

Hense ABCD is a rectangle

*-Answered by Akki chauhan* On 15 January 2019:09:05:05 AM

**Question 3.** **Asked on :**09 January 2019:09:54:18 AM

Prove that if the chords are equal then the subtend angle at the center are equal?

*-Added by Master Purushottam* **Mathematics** » **Circles**

**Answer:**

Given : In a circle C(O,r) , ∠AOB = ∠COD

To Prove : Chord AB = Chord CD .

Proof : In △AOB and △COD

AO = CO [radii of same circle]

BO = DO [radii of same circle]

∠AOB = ∠COD [given]

⇒ △AOB ≅ △COD [by SAS congruence axiom]

⇒ Chord AB = Chord CD [c.p.c.t]

*-Answered by Akki chauhan* On 13 January 2019:01:04:33 PM

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