1.

The equation of tangents drawn from the origin to the circle`x^2+y^2-2rx-2hy+h^2=0`A. `h=pmr`B. `h= pm 2r`C. `h^(2)+r^(2)=1`D. `h=pm 3r`

Answer» Correct Answer - A
The combined equation of the tangents drawn from (0, 0) to `x^(2)+y^(2)-2rx-2hy+h^(2)=0`, is
`(x^(2)+y^(2)-2rx-2hy+h^(2))h^(2)=(-rx-hy+h^(2))^(2)`
This equation represents a pair of perpendicular straight lines if
Coeff. Of `x^(2)+ `Coeff. off `y^(2)=0`
`rArr 2h^(2)-r^(2)-h^(2)=0rArr r^(2)=h^(2)rArr r = pm h`.


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