You didn't give us the equation, but circle equations are in the form;
(x-h)^2 + (y-k)^2 =r^2 where h and k are the x and y coordinate of the center and r is the radius of the circle squared.


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Therefore, the value of n is 30.


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Hence verified.

Because 6 * 8 + ( - 2 )* 24 = 48 - 48 = 0 , the vectora u and v are orthogonal ;
Two vectors are orthogonal if their dot product is zero.<span />
I believe the answer is 78.54 , D