百度作业网三角函数 (22 12:26:25)
来源：学生作业帮 编辑：百度作业网作业帮 分类：数学作业 时间：2024/05/03 20:01:40
三角函数 (22 12:26:25)
已知sin α=2cos α 求:
①(sin α-4cos α)/(5sin α+2cos α)
②sin2 α+2sin αcos α的值
已知sin α=2cos α 求:
①(sin α-4cos α)/(5sin α+2cos α)
②sin2 α+2sin αcos α的值
sin α=2cos α ,tana=2
①(sin α-4cos α)/(5sin α+2cos α)
=(tana-4)/(5tana+2)
=-1/6
sin^2 α+2sin αcos α
=(sin^2 α+2sin αcos α)/(sin^2a+cos^2a)
=(tan^2a+2tana)/(tan^2a+1)
=8/5
①(sin α-4cos α)/(5sin α+2cos α)
=(tana-4)/(5tana+2)
=-1/6
sin^2 α+2sin αcos α
=(sin^2 α+2sin αcos α)/(sin^2a+cos^2a)
=(tan^2a+2tana)/(tan^2a+1)
=8/5