If the straight line y=mx+c touches the circle x2+y2−2x−4y+3=0 at the point (2,3), then c=
A
−3
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B
4
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C
5
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D
−2
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Solution
The correct option is C5 x2+y2−2x−4y+3=0centre,(+1,+2)radius=√12+22−3=√2linetouchesat(2,3)∴Slopeofnormal=3−22−1=1∴Slopeoftangent=−1y=−x+clinepassesthrough(2,3)so2+3=corc=5