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Find the slope of a common tangent to the ellipse `(x^2)/(a^2)+(y^2)/(b^2)=1`and aconcentric circle of radius `rdot`A. `tan^(-1),sqrt((r^(2)-b^(2))/(a^(2)-r^(2))`B. `sqrt((r^(2)-b^(2))/(a^(2)-r^(2))`C. `((r^(2)-b^(2))/(a^(2)-r^(2)))`D. `sqrt((a^(2)-r^(2))/(r^(2)-b^(2)))` |
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Answer» Correct Answer - B `y=mx+sqrt(a^(2)m^(2)+b^(2))` is tangent to the ellipse. Equation of concentric circle be `x^(2)+y^(2)=r^(2)` `y =mx pm rsqrt(1+m^(2))` ia tangent to the circle. `therefore rsqrt(1+m^(2))=sqrt(a^(2)m^(2)+b^(2))` `(1+m^(2))r^(2)=a^(2)m^(2)+b^(2)` `m^(2)(r^(2)-a^(2))=b^(2)-r^(2)` `therefore m=sqrt((r^(2)-b^(2))/(a^(2)-r^(2))` |
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