- Proofs Without WordsPolygonal Number 多邊形數Centered Polygonal Number 中心多邊形數Triangular Number 三角形數Sum of First n Odd Numbers 首n個奇數之和Sum of First n Squares 首n個平方數之和Sum of First n Cubes 首n個立方數之和Sum of Squares & Perfect Square 平方和與完全平方Difference of Two Squares 平方差 (2)Difference of Two Squares 平方差 (1)Area of TrapeziumProof without words: Cosine Rule (餘弦公式)Interior & Exterior Angles of Triangles 三角形內角和及外角Two SquaresProof of Pythagoras Theorem(1) 畢氏定理的証明(1)Viviani's TheoremFeynman's TriangleArea of Circles 圓面積
