F.5 Maths circle
In the figure, X and Y are the centres of two equal circles. AR touches the circle at P and Q. AR passes through X and touches the circle with centre Y at D. If the two circles touch each other at S. Find θ.
D. It cannot be determined.
My finding: http://postimg.org/image/62a1ejsab/
I cannot find the actual value of θ. Is the answer is D or any things I have missed
so that the answer should be A,B or C?
Please help. Thank you!
RE 邊位都好 ：
Why XYQP is rectangle?
- 邊位都好Lv 55 年 前最佳解答
XYQP is a rectangle, let XP be r, so XY is 2r.Triangle DXY is a right-angled triangle with right angle XDY.
As DY is also having the length r, so,sin θ＝DY/XY＝r/2r＝1/2therefore, θ＝30° ⋯⋯ (C)
2015-01-17 00:29:46 補充：
They are two equal circles, and AR touch these two circles at P, Q.
So, XP丄AR and YQ丄AR, that is, XYQP is a rectangle.
- YA HOO！知識＋管理員Lv 65 年 前
You can draw XY and DY only
It may be the easiest way to find θ by using sin θ