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Math Help - cartesian plane

  1. #1
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    cartesian plane

    find the radius of a circle with center at (-2, 1), if a chord length of 10 is bisected at (-3, 0).

    can you help me with this one? i think ill know how to solve it if i know the drawing.

    by the way, answer is 33 or 5.196 according to our prof.
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by proview View Post
    find the radius of a circle with center at (-2, 1), if a chord length of 10 is bisected at (-3, 0).

    can you help me with this one? i think ill know how to solve it if i know the drawing.

    by the way, answer is 33 or 5.196 according to our prof.
    yes, that's the answer. i wish i had my graphing software and stuff on this PC so that i could show you the diagram.

    anyway, plot the center, and draw a line connecting it to (-3,0). the chord is perpendicular to this line. so draw that (the line you drew first is the perpendicular bisector of the chord). then use the formula \text{chord length} = 2 \sqrt{r^2 - d^2}, with r and d as shown here. you can figure out the value of d using Pythagoras' theorem, and then just solve the equation for r
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  3. #3
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    thanks for help. i got the drawing and realized that you can use Pythagorean theorem to solve it all the way.
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