927Crux 2849, proposed by Toshio Seimiya, Kawasaki, Japan
In a convex quadrilateralABCD,wehave∠ABC=∠BCD= 120◦.
Suppose thatAB^2 +BC^2 +CD^2 =AD^2. Prove thatABCDhas an
inscribed circle.
ann
(Ann)
#1
927Crux 2849, proposed by Toshio Seimiya, Kawasaki, Japan
In a convex quadrilateralABCD,wehave∠ABC=∠BCD= 120◦.
Suppose thatAB^2 +BC^2 +CD^2 =AD^2. Prove thatABCDhas an
inscribed circle.