第1个回答 2013-06-12
sin15°=sin(45° - 30°)
=sin45°cos30° - cos45°sin30°
=√2/2 * √3/2 - √2/2 * 1/2
=(√6 - √2)/4
cos15°=cos(45° - 30°)
=cos45°cos30°+sin45°sin30°
=√2/2 * √3/2+√2/2 * 1/2
=(√6+√2)/4
tan15°=sin15°/cos15°
=[(√6-√2)/4] / [(√6+√2)/4]
=(√6-√2) / (√6+√2)
=(√6-√2)^2 / (6 - 2)
=(6+2 - 4√3) / 4
=2 - √3本回答被网友采纳