Any ideas how to solve this? I couldn´t, don´t know if it´s right.
Circle X has chord AB that intersects radius XC in point D and angle XDB is 90°. If AB=12 and DC=2. What is the circumference of the circle?
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Circle and Chord
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kinda hard to explain without a diagram, but.....
We know that XC is the radius. Since the chord intersects at a 90 degree angle, we know that AD=6.
DC=2
Therefore XD = XC -2
note XC is also the radius of the circle, so XD = R - 2
Note that XA is also the radius.
Using Pythagoras:
XD^2 + 6^2 = XA ^2
(r-2)^2 + 36 = r^2
r^2 - 4r + 4 + 36 = r^2
work that out and you get r = 10
Circumference of a circle is defined by
2πr
=2π(10)
=20π
DAMN IT, someone beat me to it!
We know that XC is the radius. Since the chord intersects at a 90 degree angle, we know that AD=6.
DC=2
Therefore XD = XC -2
note XC is also the radius of the circle, so XD = R - 2
Note that XA is also the radius.
Using Pythagoras:
XD^2 + 6^2 = XA ^2
(r-2)^2 + 36 = r^2
r^2 - 4r + 4 + 36 = r^2
work that out and you get r = 10
Circumference of a circle is defined by
2πr
=2π(10)
=20π
DAMN IT, someone beat me to it!
- dumb.doofus
- Master | Next Rank: 500 Posts
- Posts: 435
- Joined: Sat Sep 27, 2008 2:02 pm
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It can't be both are equal.. recheck the steps what you are doing.. or post the steps here..PAB2706 wrote:why is the answer different when i take XB=XD+2
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