The tangents drawn from the origin to the circle x2+y2−2rx−2hy+h2=0 are perpendicular, if
A
h=±r
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B
h=±2r
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C
h2+r2=1
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D
h=±3r
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Solution
The correct option is Bh=±r The combined equation of the tangents that can be drawn from (0,0) to x2+y2−2rx−2hy+h2=0, is SS1=T2 (x2+y2−2rx−2hy+h2)h2=(−rx−hy+h2)2 This equation represents a pair of perpendicular straight lines if Coeff. of x2 + Coeff. of y2=0 ⇒2h2−r2−h2=0⇒r2=h2 ⇒r=±h Ans: A