The figure shows a circle with center O and diameter PQ. Point R lies on the circumference of the circle such that PR=QR and PR= 4 cm.The radius of the given circle (correct to two decimal places) is
A
2.83 cm
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B
4cm
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C
2cm
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D
8cm
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Solution
The correct option is A 2.83 cm ∠PRQhasbeensubtendedbythediameterPQtothecircumferenceatR.∴∠PRQisanangleinthesemicircle.∴∠PRQ=90osincetheangleinasemicircle=90o.SoΔPQRisrightangledwithPQashypotenuse.ApplyingPythagorastheorem,wehave,PQ=√PR2+QR2=√42+42cm=√32cm.∴theradiusOP=OQ=12diameterPQ=√322cm=2.83cm.Ans−OptionA.