Geo4.65

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Find the equation of the tangents drawn from (10,4)to the circle x^{2}+y^{2}=25\,

Given circle is S\equiv x^{2}+y^{2}-25=0\,

For the given point (10,4)

S_{1}\equiv 10x+4y-25,S_{{11}}\equiv 91\,

Equation to the pair of tangents from the origin to S=0 is

[S_{1}]^{2}=SS_{{11}}\,

(10x+4y-25)^{2}=91(x^{2}+y^{2}-25)\,


Main Page:Geometry:Circles