Question

If circumference of a circle x^2 +y^2 -6x+2y+c =0 be 6pie units, find c

Answer 1

Circumference = 2× pie × r

Circumference = 6pie

Thus ;

2pie × r = 6pie

r = 3

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$r = \frac{1}{2} \sqrt{ ({ - 6})^{2} + {2}^{2} - c}$

$3 = \frac{1}{2} \sqrt{ 36 + 4 - c}$

$6 = \sqrt{40 - c}$

$( {6})^{2} = ({ \sqrt{40 - c} })^{2}$

$36 = 40 - c$

$c = 4$