(adsbygoogle = window.adsbygoogle || []).push({}); Show that for any quadrilateral(convex or not), the lines containing the diagonals intersect.

How would I prove this?

I know that

1) A and B are on the same side of the line CD

2) B and C are on the same side of the line DA

3) C and D are on the same side of the line AB

4) D and A are on the same side of the line BC

With this being said, is this a good proof?

Let ABCD be a quadrilateral. By condition 1 and 2 from above we know that B is in the interior of angle ADC and the ray DB intersects AC at point P. Also that A is in the interior of angle BCD and that ray CA intersects line BD at point Q. Since line DB intersect AC at point P and also at point Q, P=Q. Since P lies on AC and Q lies on BD then AC and BD have a point in common which means that the quadrilateral satisfies all the conditions of being a convex qualdrilateral also.

Thanks for the help!!

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# Homework Help: Quadrilateral help please!

Can you offer guidance or do you also need help?

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