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Tangent

☼ Tangent :–

(i) Equation of a tangent to a circle S : x² + y² = r² at point M ( x₁, y₁ ) is x₁x + y₁y = r². And equation of a normal PM is : y₁x – x₁y = 0

(ii) Equation of a tangent to a circle S : x² + y² + 2gx + 2fy + c = 0 at a point ( x, y ) is

x₁x + y₁y + g(x₁+ x) + f (y₁+ y) + c = 0

And Equation of a normal $\overleftrightarrow{PM}$ is : $\frac{x-x_1}{x_1+g} = \frac{y-y_1}{y_1+f}$