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Find the length of the chord x+2y=5\, of the circle x^{2}+y^{2}=9\,

Centre C=(0,0) and radius r=3

Distance of the line x+2y=5 from C is

d=|{\frac  {0+0-5}{{\sqrt  {5}}}}|\,

{\sqrt  {5}}\,

Lenght of the chord is

2({\sqrt  {r^{2}-d^{2}}})\,

2{\sqrt  {9-5}}\,


Hence the length of the chord is 4units.

Main Page:Geometry:Circles