[急]数:已知a为锐角,tan(派/4+a)=2.(1)求tan a的值(2)求(sin2acosa-sina)/cos2a的值　_数学解答

[急]数:已知a为锐角,tan(派/4+a)=2.(1)求tan a的值(2)求(sin2acosa-sina)/cos2a的值　

人气：461 ℃　时间：2020-05-19 18:00:35

解答

(1) tan(π/4+a)=[tan(π/4)+tana]/[1-tan(π/4)tana]=2
1+tana=2(1-tana) tana=1/3
(2) (sin2acosa-sina)/cos2a
=sina[2(cosa)^2-1]/cos2a
=sinacos2a/cos2a
=sina=tana√[1+(tana)^2]
=√10/3