问题
填空题
化简
|
答案
∵tan60°=
=tan（81°-21°）=3 tan81°-tan21° 1+tan81°•tan21°
∴tan81°-tan21°=
（1+tan81°•tan21°）3
∴tan81°•tan21°=
（tan81°-tan21°-3 3
）3
∴tan81°tan21° tan81°-tan21°+tan300°
=tan81°tan21° tan81°-tan21°- 3
=
(tan81°-tan21°-3 3
)3 tan81°-tan21°- 3
=3 3
故答案为：3 3