作业帮15度的正切值
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15度的正切值
tan15°=2 - √¯3,约为0.2679 .
tan(15°) = 0.26794919243112
望采纳O(∩_∩)O~
解法一：cos30 °= √¯3/2
cos15 °= √¯[(1 + cos30° )/2]
sin15° = √¯[(1 - cos30° )/2]
tan15° = sin15° /cos15°
= √¯[(1 - cos30° )/(1 + cos30° )]
= √¯[(2 - √...
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解法一：cos30 °= √¯3/2
cos15 °= √¯[(1 + cos30° )/2]
sin15° = √¯[(1 - cos30° )/2]
tan15° = sin15° /cos15°
= √¯[(1 - cos30° )/(1 + cos30° )]
= √¯[(2 - √¯3)/(2 + √¯3)]
= (2 - √¯3)
解法二：作Rt△ABC，使∠A=30°∠B=90°
延长BA到D，使AD=AC，连接CD，则∠D=15°
令BG=1，则AD=AC=2，AB=√¯3。
故BD=AD+AB=2+√¯3
tan15° =tan∠D=BC/BD
=1/(2+√¯3)= (2 - √¯3)
收起
tan15°=0.2679