If tan β=n sin α cos α1−n sin2 α, then tan (α−β) is equal to
We have given
tan β=n sin α cos α1−n sin2 α
⇒ tan β=n sin α cos αsec2α−n tan2 α
⇒tan β=n tan α(1+tan2α)−n tan2 α⇒tan β=n tan α1+(1−n)tan2α
∵tan(α−β)=tanα−tanβ1+tanα.tanβ
⇒tan(α−β)=tan α−n tan α1+(1−n)tan2α1+tan α. n tan α1+(1−n)tan2α⇒tan(α−β)=tan α+(1−n)tan3α−n tan α1+(1−n)tan2α+n tan2α⇒tan(α−β)=(1−n)tan α+(1−n)tan3α1+(1−n)tan2α+n tan2α⇒tan(α−β)=(1−n).tan α.(1+tan2α)1+tan2α⇒tan(α−β)=(1−n)tan α
Hence option(b) is correct answer.