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 = (1)/(2) \sqrt{ ({ - 6})^(2) + {2}^(2) - c} \\`

`3 = (1)/(2) √( 36 + 4 - c) \\`

`6 = √(40 - c)`

`( {6})^(2) = ({ √(40 - c) })^(2)`

`36 = 40 - c`

`c = 4`