已知tana=-3/4,求tan(a-π/4),tan2a的值

已知tana=-3/4,求tan(a-π/4),tan2a的值
已知tana=-3/4,求tan(a-π/4),tan2a的值

已知tana=-3/4,求tan(a-π/4),tan2a的值
tan(a-π/4)
=(tana-tanπ/4)/(1+tanatanπ/4)
=(-3/4-1)/(1-3/4*1)
=-7
tan2a
=2tana/(1-tana^2)
=(-3/2)/(1-9/16)
=-24/7