1+2√¯3先算tan15° tan15° = sin15° /cos15° = √¯[(1 - cos30° )/(1 + cos30° )] = √¯[(2 - √¯3)/(2 + √¯3)] = 2 - √¯3tan15°-1/tan15°+1=2 - √¯3-（2 + √¯...