Value of s - Please help

This topic has expert replies
Source: — Problem Solving |

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 3835
Joined: Fri Apr 02, 2010 10:00 pm
Location: Milpitas, CA
Thanked: 1854 times
Followed by:523 members
GMAT Score:770

by Anurag@Gurome » Wed Feb 22, 2012 4:37 am
rjanardhanan wrote:In the figure shown, point P (-√3, 1) and Q (s, t) lie on the circle with center O.

Image

What is value of s?
Coordinates of O = (0, 0) and that of P are (-√3, 1)
Slope of OP = (1 - 0)/(-√3 - 0) = -1/√3, which implies slope of OQ is √3 since product of slopes of perpendicular lines is -1.
Slope of OQ = (t - 0)/(s - 0) = t/s = √3/1, which clearly implies that t = √3 and [spoiler]s = 1[/spoiler]
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)

Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/

User avatar
Senior | Next Rank: 100 Posts
Posts: 30
Joined: Tue Dec 20, 2011 2:11 pm
Thanked: 4 times
Followed by:1 members

by Lasve » Fri Apr 27, 2012 11:13 am
Image

I Solved it in a different way.
First of all it's obvious that point P and Q creates two triangles with the x and y Axis.
I drew thus triangles and name the new angles respectively a & b.

we know that segment OA is √3 and PA is 1, consequently PO must be 2.
Since PO and QO are both radius of the half circle drew in the picture, they must both be 2.

since that is the classic 1: √3 : 2 right triangle that means that angle pOa must be 30 degree.
Since pOa + pOq + qOb = 180 -> 30 + 90 + qOb =180 -> qOb = 60°

Since It's obvious that qBo = 90

We now know that also riangle QBO is a right 30:60:90 Triangle,and since
qBo = 90° and QO 2
qOb = 60°, THEN Segment QB = √3
oQb = 30, then OB = 1

So the x coordinate of the point Q is s=1