Answer:
tan 4x
Step-by-step explanation:
Note the difference identity for tangent ratio is
tan(x - y) = [tex]\frac{tanx-tany}{1+tanxtany}[/tex]
Given
[tex]\frac{tan9x-tan5x}{1+tan9xtan5x}[/tex] ← in the form of the right side of the expansion, thus
= tan(9x - 5x)
= tan 4x
