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Q 7. AC and BD are chords of a circle that bisect each other. Prove that

(i) AC and BD are diameters

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Given: AC and BD are chords of a circle which bisect each other.

To prove: AC and BD are diameters.

Construction: Join AB,BC,CD,DA. 

Proof :

In ABD and CDO,
AO=OC-----(Given)\angle \mathrm{AOB}=\angle \mathrm{COD}(Verticallyoppositeangles)\mathrm{BO}=\mathrm{DO}(Given)So,\triangle \mathrm{ABD} \cong \triangle \mathrm{CDO}(BySAS)\angle \mathrm{BAO}=\angle \mathrm{DCO} 
 ---(\mathrm{CPCT})\angle \mathrm{BAO}and\angle \mathrm{DCO}arealternateanglesandareequal.So,A B \| D C1AlsoA D \| B C$ ---------- 2

From 1 and 2,

A+C=180
A=C
From 3 and 4,
A+A=180
2A=180
A=90

BD is the diameter of the circle.

Similarly, AC is a diameter.

Posted by

seema garhwal

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