prep-ps1-59 原谅我数学差

zdx618

In the figure above, points  and Q lie on the circle with center O.  What is the value of s ?

(A)  1/2

(B)  1 

(C)  √2

(D)  √3

(E)  √2/2

答案为b，谁能告诉我怎么做的阿？谢谢！~

ubimr

没图。

jiangmingjia

http://www.beatthegmat.com/circle-on-xy-plane-q-t26752.html

IMO B

s = 1

after every 90degrees the co-ordinates will get inverted with the sign assigned according to the quadrant in which the point lies.

For eg.,

suppose Point P was at (-2,0), then a point on the same circle 90 degrees away from that point would have been either (0,2) or (0,-2), depending on the quadrant.

Here, Point Q lies in the first quadrant, hence both 's' and 't' will be positive, and the co-ordinates of Point P will be inverted.

Hence, Q = (1,root3)
and s = 1
    

jessiecg

不懂啊~

IVANNA

哪位大侠帮忙解释一下啊 我也不会