se7en14
If circle O is inscribed inside of equilateral triangle T, which of the following expresses the ratio of the radius of circle O to one of the sides of triangle T?
1 to 2
1 to \(\sqrt{2}\)
1 to \(\sqrt{3}\)
1 to \(2\sqrt{2}\)
1 to \(2\sqrt{3}\)
No diagram is provided.
Dear
se7en14,
I'm happy to help.
Here's a diagram:
Attachment:
equilateral with inscribed circle.JPG [ 15.35 KiB | Viewed 5728 times ]
Point E is the center of the circle, so DE is the radius. Let's say that DE = 1. Notice that triangle DEC is a 30-60-90 triangle, with a 30 degree angle at C and a 60 degree angle at E. For more on the properties of this triangle, see:
https://magoosh.com/gmat/2012/the-gmats- ... triangles/The sides have ratios of 1-2-sqrt(3). Here:
DE = 1
CE = 2
DC = \(\sqrt{3}\)
Now, notice that DC is half the side, because D is a midpoint of the side. This means
AC = 2*(DC) = \(2*\sqrt{3}\)
That's the length of the side. Therefore,
radius:side = 1: \(2*\sqrt{3}\)
Answer =
(D)Does all this make sense?
Mike