250 pages with 60 laboratory lessons and solutions in Algebra and Geometry suitable for use in a high school plane geometry course. Students explore and discover geometric postulates and theorems in Geometry and use their discoveries and observations to write proofs and develop solutions to related algebraic and geometric problems that are provided with each lab. It is an indispensable companion to any standard secondary geometry course. Topics include a complete visual introduction to the postulational system of geometry, the geometric theorems involved with congruence, quadrilaterals, proportional line segments, special triangles and fundamental locus theorems. This book requires the use of the Geometer's Sketchpad, Version 5, a registered trademark of Key Curriculum Press. The book was supported by Key Curriculum Press with a grant to the authors. This is a revised version of the previously published "Explorations and Discoveries in Mathematics Using the Geometer's Sketchpad Version 4, Volume 3" 2007.