已知3π/4
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已知3π/4已知3π/4已知3π/4tanα+1/tanα=-10/3,tana=-3,或tana=-1/3[5sin²a/2+8sina/2cosa/2+11cos²a/2-8]
已知3π/4
已知3π/4
已知3π/4
tanα+1/tanα=-10/3,tana=-3,或tana=-1/3
[5sin²a/2+8sina/2 cosa/2+11cos²a/2-8]/√2sin(a-π/4)
=[5sin²a/2+5cos²a/2+8sina/2 cosa/2+6cos²a/2-8]/√2[sinacos(π/4)-cosasin(π/4)]
=[-3+4sina+6cos²a/2]/(sina-cosa)
=(4sina+3cosa)/(sina-cosa)
=(4tana-3)/(tana-1)
当tana=-3时
=-15/(-4)
=15/4
当tana=-1/3时
＝13/4