Take the 2-minute tour ×
Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

We denote $P= WX \cap YZ$ to mean point $P$ is the intersection of lines $WX$ and $YZ$.

The problem is about pascal's theorem: Let $ABCD$ be a cyclic quadrilateral. Let the tangent lines at A and at B to the circumcircle of ABCD meet at R. Let the tangent lines at C and at D to the circumcircle of ABCD meet at S. Let $T=AD \cap BC$ and $U=AC \cap BD$. Prove that $R,S,T,U$ are collinear.

share|improve this question
    
Please try to follow the site's guidelines. Simply stating a problem and expecting an answer is not the way it's done. Please read: math.stackexchange.com/tags/homework/info –  Fly by Night May 5 '13 at 17:57

1 Answer 1

up vote 2 down vote accepted

Considering $(A,A,C,B,B,D)$, what do you get?

share|improve this answer
    
we have T,U and R are collinear. Then we apply Pascal's theorem again to $(A,D,D,B,C,C)$ to get T,U,S collinear? Thank you very much! –  Ishigami May 5 '13 at 18:17

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.