急啊:tan(a+π/4)+tan(a+3π/4)=2tan2atan(a+π/4)+tan(a+3π/4)=2tan2a在线急求解答! 谢谢各位大虾!

来源:学生作业帮助网 编辑:作业帮 时间:2024/04/29 23:52:34
急啊:tan(a+π/4)+tan(a+3π/4)=2tan2atan(a+π/4)+tan(a+3π/4)=2tan2a在线急求解答!  谢谢各位大虾!

急啊:tan(a+π/4)+tan(a+3π/4)=2tan2atan(a+π/4)+tan(a+3π/4)=2tan2a在线急求解答! 谢谢各位大虾!
急啊:tan(a+π/4)+tan(a+3π/4)=2tan2a
tan(a+π/4)+tan(a+3π/4)=2tan2a
在线急求解答! 谢谢各位大虾!

急啊:tan(a+π/4)+tan(a+3π/4)=2tan2atan(a+π/4)+tan(a+3π/4)=2tan2a在线急求解答! 谢谢各位大虾!
证明:
∵tan(a+π/4)=(tana+tanπ/4)/(1-tana*tanπ/4)=(tana+1)/(1-tana)
tan(a+3π/4)=(tana+tan3π/4)/(1-tana*tan3π/4)=(tana-1)/(1+tana)
∴tan(a+π/4)+tan(a+3π/4)
=(tana+1)/(1-tana)+(tana-1)/(1+tana)
=[(tana+1)²-(tana+1)²]/(1-tan²a)
=4tana/(1-tan²a)
∵tan2a=2tana/(1-tan²a)
∴tan(a+π/4)+tan(a+3π/4)=2tan2a