Proof and Computation in Geometry -- Automation of Geometry: Theorem Proving, Diagram -- Generation, and Knowledge Management -- Improving Angular Speed Uniformity by C1 Piecewise Reparameterization -- Extending the Descartes Circle Theorem for Steiner n-Cycles -- Equation Systems with Free-Coordinates Determinants -- Formal Proof in Coq and Derivation of an Imperative Program to Compute Convex Hulls -- Realizations of Volume Frameworks -- Rigidity of Origami Universal Molecules -- Algebraic Analysis of Huzita’s Origami Operations and Their Extensions -- On the Formal Analysis of Geometrical Optics in HOL -- Preprocessing of the Axiomatic System for More Efficient Automated Proving and Shorter Proofs.

This book constitutes the thoroughly refereed post-workshop proceedings of the 9th International Workshop on Automated Deduction in Geometry, ADG 2012, held in Edinburgh, UK, in September 2012. The 10 revised full papers presented together with 2 invited papers were carefully selected during two rounds of reviewing and improvement from the lectures given at the workshop. The conference represents a forum to exchange ideas and views, to present research results and progress, and to demonstrate software tools at the intersection between geometry and automated deduction; the scope of the ADG 2012 moreover has been expanded to cover topics in dynamic geometry.