Math Is Fun Forum

lovealgebranotgeometry

Member

Registered: 2017-04-21

Posts: 13

I have spent hours on this and can not figure this out.

I am given a picture of circle where AC is a diameter of the circle.  AB = 12, mDC = 40, mAG = 80. AB||DG.  I am asked to find the diameter of the circle and the measure of all arcs as well as find EF.  Can someone please let me know how I should approach solving this problem?  I can not figure out how to insert the picture on my post.

Thanks bobbym

Last edited by lovealgebranotgeometry (2017-04-22 00:01:55)

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: I have spent hours on this and can not figure this out.

Hi;

Upload your image to Imgur.com or any other image hosting site. From there paste the image location between the image tags.

Did you get your image to Imgur? Need help to get it from there to here?

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

lovealgebranotgeometry

Member

Registered: 2017-04-21

Posts: 13

Re: I have spent hours on this and can not figure this out.

I uploaded it to Imgur and pasted the link, however, the image is not showing.

http://imgur.com/LIaxPoj

Last edited by lovealgebranotgeometry (2017-04-22 00:37:31)

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: I have spent hours on this and can not figure this out.

Hi;

I have put it in there for you.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

lovealgebranotgeometry

Member

Registered: 2017-04-21

Posts: 13

Re: I have spent hours on this and can not figure this out.

Thank you!!!

lovealgebranotgeometry

Member

Registered: 2017-04-21

Posts: 13

Re: I have spent hours on this and can not figure this out.

My teacher made the problem.  This is the original picture.

Last edited by lovealgebranotgeometry (2017-04-22 05:05:29)

lovealgebranotgeometry

Member

Registered: 2017-04-21

Posts: 13

Re: I have spent hours on this and can not figure this out.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: I have spent hours on this and can not figure this out.

I have left the important posts so that you will be able to continue with someone else.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

lovealgebranotgeometry

Member

Registered: 2017-04-21

Posts: 13

Re: I have spent hours on this and can not figure this out.

Thank you for all your great assistance.  I hope to be able to figure this out.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,634

Re: I have spent hours on this and can not figure this out.

hi lovealgebranotgeometry

Welcome to the forum.

Quick clarification needed as I don't use the 'measure of an arc' notation.  When you say the measure of an arc is 40, do you mean that it is 40 units long, or that the arc makes an angle of 40 degrees at the centre of the circle.  In your work above, you appear to mean the latter.

Thanks,

Bob

LATER EDIT:

Haven't worked out EF yet.  I'm working on similar triangles.

Last edited by Bob (2017-04-22 20:53:16)

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

lovealgebranotgeometry

Member

Registered: 2017-04-21

Posts: 13

Re: I have spent hours on this and can not figure this out.

When I say the arc is 40 I mean that it makes an angle of 40 degrees.  It was suggested that I find EF by using auxiliary lines and trig.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,634

Re: I have spent hours on this and can not figure this out.

hi lovealgebranotgeometry

You can get BC, and GD with trig. and all the lengths of FEC as a fixed fraction of ABC.

After that it starts to get tricky.  This theorem may help:

http://www.mathisfunforum.com/viewtopic … 92#p368592

but so far that has only led me to some complicated algebra which might work if I kept going for long enough.

Oh yes, I forgot.  Mark the centre and some radii.

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

lovealgebranotgeometry

Member

Registered: 2017-04-21

Posts: 13

Re: I have spent hours on this and can not figure this out.

I have BC as 12 rad 3 but I can not figure out how to find GD with Trig.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,634

Re: I have spent hours on this and can not figure this out.

If the centre is point H, you can enter all the angles around H and hence get angle HDG in an isosceles triangle.  So splitting it in half gives you a 90 angle for some trig.

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

lovealgebranotgeometry

Member

Registered: 2017-04-21

Posts: 13

Re: I have spent hours on this and can not figure this out.

By using trig would  you be able to find that HF equals about 4.1 ?

lovealgebranotgeometry

Member

Registered: 2017-04-21

Posts: 13

Re: I have spent hours on this and can not figure this out.

I have come up with ~ 3.95 for EF.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,634

Re: I have spent hours on this and can not figure this out.

I made a drawing using 'Sketchpad', and got about 3.6

That's not to say I'm disagreeing with your answer.  I may not have been sufficiently accurate.  Please post your method.

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

lovealgebranotgeometry

Member

Registered: 2017-04-21

Posts: 13

Re: I have spent hours on this and can not figure this out.

thickhead

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Registered: 2016-04-16

Posts: 1,086

Re: I have spent hours on this and can not figure this out.

Due to symmetry.

Last edited by thickhead (2017-04-23 18:04:55)

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{1}Vasudhaiva Kutumakam.{The whole Universe is a family.}
(2)Yatra naaryasthu poojyanthe Ramanthe tatra Devataha
{Gods rejoice at those places where ladies are respected.}

thickhead

Member

Registered: 2016-04-16

Posts: 1,086

Re: I have spent hours on this and can not figure this out.

My answer for EF is 

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{1}Vasudhaiva Kutumakam.{The whole Universe is a family.}
(2)Yatra naaryasthu poojyanthe Ramanthe tatra Devataha
{Gods rejoice at those places where ladies are respected.}

lovealgebranotgeometry

Member

Registered: 2017-04-21

Posts: 13

Re: I have spent hours on this and can not figure this out.

So EF = 6.363041 not the 3.95 I originally calculated?

lovealgebranotgeometry

Member

Registered: 2017-04-21

Posts: 13

Re: I have spent hours on this and can not figure this out.

meant 3.630  I think I see my error now.  Thanks so much.  I have spent countless hours on this.