- #1

PF PotW Robot

The sum of the angles ##A## and ##C## of a convex quadrilateral ##ABCD## is less than ##180^\circ##.

Prove that ##AB\cdot CD+AD \cdot BC <AC(AB+AD)##

(PotW thanks to our friends at MHB)

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- Thread starter PF PotW Robot
- Start date

- #1

PF PotW Robot

The sum of the angles ##A## and ##C## of a convex quadrilateral ##ABCD## is less than ##180^\circ##.

Prove that ##AB\cdot CD+AD \cdot BC <AC(AB+AD)##

(PotW thanks to our friends at MHB)

- #2

fresh_42

Mentor

- 15,384

- 13,411

Hint: Ptolemy's theorem and Ptolemy's inequality.

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