1.

We know thatTan (x+y)=tanx+tany/1+tanx tanyPut y =xTan(X+x)= tanx+tanx /1-tanx tanyTan2x= 2tanx/1-tan2x

Answer»

To prove sin2x = \(\frac{2tanx}{1+tan^2x}\)

Let us start from RHS and prove it equal to LHS.

RHS = \(\frac{2tanx}{1+tan^2x}\) 

\(\frac{2tanx}{sec^2x}\), as 1 + tan2x  = sec2 x,identity

⇒ \(\frac{2\Big(\frac{sinx}{cosx}\Big)}{\frac{1}{cos^2x}}\)

⇒2sinxcosx = sin2x as per sin2x=2sinxcosx identity



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