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# Help with "Circles"

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### #81 Maledicent Posted Apr 26, 2012 - 21:55

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I still don't understand how to find the angles of the triangle AOP'. Can someone please help me? I figured out angle O, but now I'm stuck trying to find angle P'

Edited by Maledicent, Apr 26, 2012 - 21:56.

### #82 SymphonyOfSouls Posted Apr 27, 2012 - 09:01

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I still don't understand how to find the angles of the triangle AOP'. Can someone please help me? I figured out angle O, but now I'm stuck trying to find angle P'

If you're using non right-angled trig, you'll need to make use of another rule (used in nra trig) besides the cosine rule to work out P'. That's the best I can do without directly stating what you need to use!

### #83 SymphonyOfSouls Posted Apr 27, 2012 - 09:04

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I'm completely stumped on the limitations. I have one limitation, involving what happens when r is double or more OP - there's no triangle, just a straight line, though OP' can still be calculated correctly by my general statement in this situation so I'm unsure if it's a true limitation...but it's the best I've got. Can anybody point me in the right direction?

### #84 bader Posted Apr 27, 2012 - 13:56

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Guys can anyone send me the answers please? My IA is due after tomorrow (Sunday) and i don't know how to solve it at alll !!

### #85 travisjames95 Posted Apr 30, 2012 - 00:54

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For the first part I got the General statement: OP' = r/OP

For the SECOND part this is what I got..... Tell me if I'm wrong or if you got different answers.... cuz idk what the general statement is from this...?? how do I find it?

when OP=2.....
r=2
A and O =60.0
P=60
a or OP'= 2

r=3
A and O = 41.4
P=97.2
a or OP'= 4.5

this one I don't understand either...
r=4
A and O = 0
P=180? etc.....????

Edited by travisjames95, Apr 30, 2012 - 01:14.

### #86 Hakeem Posted May 03, 2012 - 12:23

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Guys what do they mean by "vary the position of P".
P.S: It cant be the raduis OP beacause I already did that

### #87 ibfrustratesme Posted May 06, 2012 - 15:22

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I have to hand in my IA in 13 hours and i really do not have a single clue how to work this out ! I really need help !

### #88 reallyhatesib Posted May 17, 2012 - 13:43

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Hello, I really need help in thinking of a general statement for OP'. I have done the first two task. But then when it comes to using tech, I'm blank. HELP!

### #89 ILikeTurtles Posted May 19, 2012 - 08:45

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I still don't understand how to find the angles of the triangle AOP'. Can someone please help me? I figured out angle O, but now I'm stuck trying to find angle P'

If you're using non right-angled trig, you'll need to make use of another rule (used in nra trig) besides the cosine rule to work out P'. That's the best I can do without directly stating what you need to use!

You actually don't need to use another rule other than the cosine rule. Well I didn't . But you have to look at the different triangles you have and how they relate so that you can find the angle P'

### #90 ILikeTurtles Posted May 19, 2012 - 09:06

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Description level 5 (max) in Criterion C is "The student tests the validity of the general statement by considering further examples".
What exactly are 'further examples' in this case? Is it just that you solve this with similarities and trigonometric approach or is it something else? Could somebody direct me, if it's something else?

I think that they want you to just take different values of OP and r and see how it affects OP'. In the question it says "Use technology to investigate other values of r and OP." So you can do so using whatever program/software you have been using.

### #91 aweffingsome Posted May 25, 2012 - 05:09

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can somebody tell me how to do the technology and op' general statement part?
I found the general statement for the first two parts but how do you go about the technology part? I know we have to use geogebra, atleast im using that, but what after that? Im stuck :|
How is it different from the first two? cause even then we found the general statement for OP'.

Nevermind that, it was just me being stupid

Edited by aweffingsome, May 25, 2012 - 13:14.

### #92 Beowulf Posted May 27, 2012 - 19:27

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Dude if you're still struggling with it, I am doing it now and you just use sine cosine rule to find one angle, then you use the sine rule to find OP'.

Hope I helped

### #93 Beowulf Posted May 30, 2012 - 17:46

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Listen, no we never assume they are parallel, why would you say such a thing! listen, we know that AO and AP' are always equal since they are the radii of Circle (C3), using cosine rule we can find angle AOP' , since triangle AOP' is an isosceles triangle then angle AOP' is equal to angle AP'O. Using this fact we find angle OAP' , then we use angle OAP' to find the length of the side OP'!! its really simplw once you get it man! try sketching with a pencil or I advice you to use GeoGebra! (AWESOME software)

### #94 Beowulf Posted May 30, 2012 - 17:49

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Hey people listen, I need a way to algebraically prove (analytically) that OP'=r2/OP ...... I am sure it is possible I just cannot find the way! can anyone help?!

### #95 jsm_95 Posted May 31, 2012 - 01:06

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ugh, stuck on finding scope and limitations, anybody want to offer some help?

Also what technology can be used for part 3?

### #96 Nana95 Posted Jun 01, 2012 - 13:37

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Can anybody tell me how we should take abt the aim??
are we supposed to explain it??

thanks

### #97 Nana95 Posted Jun 01, 2012 - 13:39

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### #98 jsm_95 Posted Jun 01, 2012 - 22:17

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what program are you using?

### #99 jsm_95 Posted Jun 03, 2012 - 15:26

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does P' need to be between points O and P, or just on the same line as OP? The IA states "The point P' is the intersection of C3 with (OP)" is the fact that OP is in brackets significant? Thanks

### #100 nr1RockStar Posted Jun 07, 2012 - 22:52

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Hey people listen, I need a way to algebraically prove (analytically) that OP'=r2/OP ...... I am sure it is possible I just cannot find the way! can anyone help?!

Use the distance formula that should help