In the xy-plane , line l intersects a circle with center : GMAT Data Sufficiency (DS)
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In the xy-plane , line l intersects a circle with center

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In the xy-plane , line l intersects a circle with center [#permalink]

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19 Aug 2013, 10:16
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In the xy-plane, line l intersects a circle with center at origin. Is the slope of line l equal to zero?

(1) Line l passes through second quadrant.

(2) Line l is perpendicular to the tangent of the circle.
[Reveal] Spoiler: OA

Last edited by Bunuel on 17 Jul 2014, 10:58, edited 1 time in total.
Edited the OA.
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Re: In the xy-plane , line l intersects a circle with center [#permalink]

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19 Aug 2013, 11:04
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innocous wrote:
In the xy-plane , line l intersects a circle with center at origin.Is the slope of line l equal to zero?

1) line l passes through second quadrant.

2) line l is perpendicular to the tangent of the circle.

ALL LINES WHICH ARE PERPENDICULAR TO TANGENT WILL PASS THROUGH CENTRE.

IMO C.

SEE DIAG FOR EXPLANATION.
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Re: In the xy-plane , line l intersects a circle with center [#permalink]

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22 Aug 2013, 03:47
In the xy-plane , line l intersects a circle with center at origin.Is the slope of line l equal to zero?

1) line l passes through second quadrant.
2) line l is perpendicular to the tangent of the circle.

FS1: Line l passing through second quadrant and intersecting the circle can be either parall to x-axis(in which case its slope is 0) or not parallel to x-axis(slope not eual to 0). Hence insufficient.
FS2: Line which is perpendicular to the tangent must pass thought centre (since angle betwwen radius and point of contact of tangent to a circle is 90 degrees). Hence, the line can have multiple possibilities for its slope (including 0 and infinity when the line is parallel to x or y axis respectively). Not sufficient.

Combining the above two, the only possibility is when the slope is negatice but not zero (x-axis is not in II quadrant). Hence slope iof line l is not zero for any case.
Sufficient. So answer should be C.
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Re: In the xy-plane , line l intersects a circle with center [#permalink]

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17 Jul 2014, 10:15
zerosleep wrote:
In the xy-plane , line l intersects a circle with center at origin.Is the slope of line l equal to zero?

1) line l passes through second quadrant.
2) line l is perpendicular to the tangent of the circle.

FS1: Line l passing through second quadrant and intersecting the circle can be either parall to x-axis(in which case its slope is 0) or not parallel to x-axis(slope not eual to 0). Hence insufficient.
FS2: Line which is perpendicular to the tangent must pass thought centre (since angle betwwen radius and point of contact of tangent to a circle is 90 degrees). Hence, the line can have multiple possibilities for its slope (including 0 and infinity when the line is parallel to x or y axis respectively). Not sufficient.

Combining the above two, the only possibility is when the slope is negatice but not zero (x-axis is not in II quadrant). Hence slope iof line l is not zero for any case.
Sufficient. So answer should be C.

The 2nd statement does not imply that the line l has to pass through the tangent point. It could be any parallel line perpendicular to the tangent.

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Re: In the xy-plane , line l intersects a circle with center [#permalink]

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17 Jul 2014, 10:57
faamir wrote:
zerosleep wrote:
In the xy-plane , line l intersects a circle with center at origin.Is the slope of line l equal to zero?

1) line l passes through second quadrant.
2) line l is perpendicular to the tangent of the circle.

FS1: Line l passing through second quadrant and intersecting the circle can be either parall to x-axis(in which case its slope is 0) or not parallel to x-axis(slope not eual to 0). Hence insufficient.
FS2: Line which is perpendicular to the tangent must pass thought centre (since angle betwwen radius and point of contact of tangent to a circle is 90 degrees). Hence, the line can have multiple possibilities for its slope (including 0 and infinity when the line is parallel to x or y axis respectively). Not sufficient.

Combining the above two, the only possibility is when the slope is negatice but not zero (x-axis is not in II quadrant). Hence slope iof line l is not zero for any case.
Sufficient. So answer should be C.

The 2nd statement does not imply that the line l has to pass through the tangent point. It could be any parallel line perpendicular to the tangent.

You are right the answer must be E:
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Re: In the xy-plane , line l intersects a circle with center [#permalink]

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17 Jul 2014, 11:04
Bunuel,

Thank you so much for the quick response. You are the best :D
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Re: In the xy-plane , line l intersects a circle with center [#permalink]

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22 Dec 2015, 22:43
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