Q. A circle in the xy-plane has the equation x2+y2−6x−10y=2. What is the diameter of the circle?
Write Equation: Write down the given equation of the circle.The given equation is x2+y2−6x−10y=2. We need to complete the square for both x and y to bring the equation into the standard form of a circle's equation, which is (x−h)2+(y−k)2=r2, where (h,k) is the center of the circle and r is its radius.
Rearrange and Group: Rearrange the equation and group x's and y's together.Rearrange the equation as follows: x2−6x+y2−10y=2. This step is necessary to prepare for completing the square for both x and y terms.
Complete X Square: Complete the square for the x terms.To complete the square for x2−6x, we take half of the coefficient of x, which is −6/2=−3, square it, (−3)2=9, and add and subtract it inside the equation. So, we get x2−6x+9−9.
Complete Y Square: Complete the square for the y terms.Similarly, for y2−10y, we take half of the coefficient of y, which is −10/2=−5, square it, (−5)2=25, and add and subtract it inside the equation. So, we get y2−10y+25−25.
Rewrite and Simplify: Rewrite the equation with completed squares and simplify.After completing the squares, the equation becomes x2−6x+9+y2−10y+25=2+9+25. Simplify the right side: 2+9+25=36. The equation now is (x−3)2+(y−5)2=36.
Identify Radius: Identify the radius of the circle.From the equation (x−3)2+(y−5)2=36, we see that the right side, 36, represents r2, where r is the radius of the circle. Therefore, r=36=6.
Calculate Diameter: Calculate the diameter of the circle.The diameter of a circle is twice its radius. Therefore, the diameter =2×r=2×6=12.
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