tan15°=（1-cos30°）/sin20°是怎么推得的
问题描述：
tan15°=（1-cos30°）/sin20°是怎么推得的
答
是 tan 15° =(1 -cos 30°) /sin 30° = = = = = = = = =tan 15° =sin 15° /cos 15°=2 (sin 15°)^2 / (2 sin 15° cos 15°)=(1 -cos 30°) /sin 30°.= = = = = = = = =另外,tan 15° =sin 15° /cos 15°=(2 ...