From the trigonometric ratios to the addition theorem of trigonometric functions and to the properties of triangles
三角比から三角関数の加法定理,三角形の性質へ

Kiyosi Yamaguti
2005 Japan Journal of Mathematics Education and Related Fields  
doi:10.34323/mesj.46.1-2_5 fatcat:vtyooumzyfdp5ddhu74r7ofab4