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Dallasb22
if pa=10 and be=21 find bp
Is there a diagram to go with this information?
Thank you. Can we assume AP is tangent to the circle and that BE is a diameter?
Well, first thing that comes to mind (because I can't remember the tangent-chord theorems off the top of my head right now..) is that you can form a right triangle AOP with O the center of the circle and AO a radius. From there you can use Pythagoras' theorem to get the missing lengths.
It's not very direct, but will work.
How can AOP form a right triangle? I drew the line(auxillary lines) and it appears acute.
Angle AOP being acute.
Yes. Angle OAP is the right angle because tangents to a circle are always at right angles to their radii.
I think that's the preliminary proposition that is used to prove the various tangent and chord theorems. I like this website for reviewing such things: http://www.mathwarehouse.com/geometry/circle/tangent-secant-side-length.php
Line OEP is therefore the hypotenuse, and when you add OB=OA, you get BP. Yes, OA is a radius so is half the diameter BE.
Oh, that's nice, everything works out to rational numbers. Very kind of them . . .
|dw:1346780775442:dw|
I'm still not sure how to find EP?
I don't think you need EP, but did you use Pythagoras' theorem to get OP?
10(^2)+10.5(^2)=c(^2) I get 210.25???
I was going to find EP. Then add BE+EP=BP
(take square root of c^2)
Ahhh. 14.5 + 10.5 correct? Equaling 25
If you use the theorem from that website I linked to, it shows the following: |dw:1346781296754:dw| Which when you simplify and put into standard form yields the quadratic equation x^2+21x-100=0. I find that unnecessary if you don't like quadratics. Either way it includes an extra step and Pythagoras' theorem gets us there just as easily.
Yes, the solutions to that quadratic equation are x=4 and x=-25. Throw out the negative length as meaningless, and EP=4; add that to the diameter and BP=25.
Okay good. Sometimes I just need someone to make me ask myself the right questions.
Thanks for helping! I have another if you don't mind...?
I usually never bother to remember such specific theorems, I prefer to deduce everything from more basic stuff that is easy to remember.
Yes, and the PT is very easy.
Exactly, it shows up everywhere; only thing you had to remember is that tangents are perpendicular to radii.
Might as well start a new thread for your next question; maybe we can get others to jump in and add their insights as well.