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One of the lamp posts at a shopping center has a motion detector on it, and the equation [tex]\((x+16)^2+(y-13)^2=36\)[/tex] describes the boundary within which motion can be sensed.

What is the greatest distance, in feet, a person could be from the lamp and be detected?

A. 6 ft
B. 12 ft
C. 36 ft
D. 72 ft


Sagot :

To determine the greatest distance a person could be from the lamp and still be detected by the motion detector, we need to analyze the given equation of the boundary.

The given equation is:
[tex]\[ (x + 16)^2 + (y - 13)^2 = 36 \][/tex]

This equation represents the boundary of a circle in its standard form:
[tex]\[ (x - h)^2 + (y - k)^2 = r^2 \][/tex]
where [tex]\((h, k)\)[/tex] is the center of the circle and [tex]\(r\)[/tex] is the radius.

From the equation [tex]\((x + 16)^2 + (y - 13)^2 = 36\)[/tex], we can identify the following:
- The center of the circle, [tex]\((h, k)\)[/tex], is deduced by comparing it with the standard form. Thus, [tex]\(h = -16\)[/tex] and [tex]\(k = 13\)[/tex].
- The term on the right side of the equation, 36, represents [tex]\(r^2\)[/tex], which is the square of the radius.

To find the radius [tex]\(r\)[/tex], we take the square root of 36:
[tex]\[ r = \sqrt{36} = 6 \][/tex]

Therefore, the radius of the circle is 6 feet.

The greatest distance a person could be from the lamp and still be detected by the motion detector is equal to the radius of the circle.

Thus, the greatest distance is:
[tex]\[ \boxed{6 \text{ ft}} \][/tex]