If A, B, C, D are four points such that ∠BAC=30∘ & ∠BDC=60∘, then D is the center of the circle through A, B and C. The statement is
A
sometimes true
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B
false
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C
true
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D
none of the above.
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Solution
The correct option is A sometimes true Given−A,B,C&Darefourpointssuchthat∠BAC=30o&∠BDC=60o.Tofindout−ifDisthecentreofthecirclewhichpassesthroughA,B&C.Solution−∠BAC=30o&∠BDC=60o.∴∠BDC=2∠BAC.Weknowthattheanglesubtendedbyachordatthecentreofacircleisdoubletheangleatthecircumferencesubtendedbythesamechord.∴∠BDCistheangleatthecentreand∠BACistheangleatthecircumferencesubtendedbythechordBC.SoDisthecentreofthecirclewhichpassesthroughA,B&C.∴ThestatementiscorrectbyfigIButbyfigIIthisisnottrue.Sothestatementisnotalwaystrue.Ans−OptionA.