Let P = ( 1 <msqrt> 2 </msqrt> </mfrac> , 1 <msqrt>

Willow Pratt

Willow Pratt

Answered question

2022-07-13

MathJax(?): Can't find handler for document MathJax(?): Can't find handler for document Let P = ( 1 2 , 1 2 ) and Q = ( 1 2 , 1 2 ) be two vertices of a regular polygon having 12 sides such that PQ is a diameter of the circle circumscribing the polygon. Which of the following points is not a vertex of this polygon?
(A) ( 3 1 2 2 , 3 + 1 2 2 )
(B) ( 3 + 1 2 2 , 3 1 2 2 )
(C) ( 3 + 1 2 2 , 1 3 2 2 )
(D) ( 1 2 , 3 2 )
If P and Q are the end points of the diameter, it is quite clear that the equation of the circle must be
x 2 + y 2 = 1
Therefore, all the vertices must lie on this circle. Now, checking from the options, we find that every point given in the options satisfies the above equation. Now I am stuck.
How else should I tackle the sum?

Answer & Explanation

Karla Hull

Karla Hull

Beginner2022-07-14Added 20 answers

D) But how did I get that answer? Well, firstly have you drawn a picture of the diagram, with angles labelled? If so, then you’ll notice that the arg (angle from the x axis) of any point on the polygon must be 15 mod 30. The last option doesn’t satisfy this property (the angle it forms is 120 degrees).
However, another approach is to notice — again from a well drawn diagram — that the figure is symmetric in the x axis, the y axis, and the x=y line. Since the first three options are just reflections of each other in these lines, the answer must be D. Meta analysis is useful in multiple choice!
Chant6j

Chant6j

Beginner2022-07-15Added 1 answers

MathJax(?): Can't find handler for document MathJax(?): Can't find handler for document A) ( 3 1 2 2 , 3 + 1 2 2 ) ( 1 2 , 1 2 ) = 3 2
B) 3 2
C) 1 2

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