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**Joshua17****Guest**

IN quadrangle ABCD:

- inside angle near the A apex is larger than 180°

- and we know that: AB * CD = AD * BC

- point P is symetrical to point A by the BD line.

Prove that PCB and ACD are equal angles.

Can someone give the solution and explain it to me pleas?? It's important.

**darthradius****Member**- Registered: 2005-11-28
- Posts: 97

I'm having trouble visualizing what you mean...we are talking about a concave quadrangle, right?...Then P is outside of the qdrngle?

I'll keep at it and get back to you, but any sort of clarification so that I could make a picture in my head would help.

Else, if you have since solved this, I would love to see your proof.

The greatest challenge to any thinker is stating the problem in a way that will allow a solution.

-Bertrand Russell

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**Joshua17****Guest**

Yes, i think it's outside but still can't prove it maybe u did?? Veary need it...

**irspow****Member**- Registered: 2005-11-24
- Posts: 456

I'd give it a stab also, but I too am unable to imagine this figure. Did you say an INSIDE angle of greater than 180 within a QUADRANGLE? And did you mean AB*BC = CD*DA? Sorry, but I am a little confused.

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**darthradius****Member**- Registered: 2005-11-28
- Posts: 97

Ya...sorry josh...I keep trying to draw different pictures and make something with similar triangles but I cannot visualize...I'll keep at it though...

Have you come up with anything at all? A picture, even?

The greatest challenge to any thinker is stating the problem in a way that will allow a solution.

-Bertrand Russell

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**ryos****Member**- Registered: 2005-08-04
- Posts: 394

Is this an accurate representation of the problem?

El que pega primero pega dos veces.

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**Joshua17****Guest**

yeah I think that's the right picture

**ryos****Member**- Registered: 2005-08-04
- Posts: 394

Except that, isn't it the standard to put the vertex of the angle in the middle of its name? So, would "PCB" and "ACB" both have their vertex at C? That would seem to make it easier to prove that the two are equal.

Don't you love these problems where nobody knows quite what they're asking?

El que pega primero pega dos veces.

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**MathsIsFun****Administrator**- Registered: 2005-01-21
- Posts: 7,559

For Posterity: ryos' current signature reads "Yo no puedo enamorarla porque solo con mirarla se me olvida lo que voy a decir..."

"The physicists defer only to mathematicians, and the mathematicians defer only to God ..." - Leon M. Lederman

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**ryos****Member**- Registered: 2005-08-04
- Posts: 394

Cool! What does that mean?

El que pega primero pega dos veces.

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**Flowers4Carlos****Member**- Registered: 2005-08-25
- Posts: 106

it reads "I can't love her because just by looking at her i forget what i'm about to say...."

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**ryos****Member**- Registered: 2005-08-04
- Posts: 394

Close. More like, "I can't woo her because whenever I see her I forget what I was about to say..."

Edit: or perhaps even more accurate, "I can't woo her because just looking at her make me forget what I was about to say..."

*Last edited by ryos (2005-12-02 10:43:54)*

El que pega primero pega dos veces.

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**nicole06****Guest**

Flowers4Carlos wrote:

it reads "I can't love her because just by looking at her i forget what i'm about to say...."

**nicole06****Guest**

awww that is so cute you should stay with her

**KRAYZIE D****Guest**

AWWWWWW THATS SOO CUTE:)

**andre3000****Guest**

nicole06 wrote:

awww that is so cute you should stay with her

**nicole06****Guest**

what up big D

**KRAYZIE D****Guest**

NIKKI HEY WHATS UP U ARE SOOO CUTE LOL I LOVE U BUNCHIE BUNCHIE AND THATS A LOT OF LOVE

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