MathDB
Equality of angles [Iran TST 2010]

Source:

June 9, 2010
geometrycircumcirclegeometric transformationratiohomothetyradical axis

Problem Statement

Circles W1,W2W_1,W_2 intersect at P,KP,K. XYXY is common tangent of two circles which is nearer to PP and XX is on W1W_1 and YY is on W2W_2. XPXP intersects W2W_2 for the second time in CC and YPYP intersects W1W_1 in BB. Let AA be intersection point of BXBX and CYCY. Prove that if QQ is the second intersection point of circumcircles of ABCABC and AXYAXY QXA=QKP\angle QXA=\angle QKP