1.

Show that\(sin^{-1}(2x\sqrt{1-x^2})=2sin^{-1}x.\)

Answer»

Given LHS = sin-1 (2x - √ (1 – x2)) 

Let x = sin θ 

= sin-1 (2sin θ √ (1 – sin2θ)) 

We know that 1 – sin2θ = cos2θ 

= sin-1 (2 sin θ cos θ) 

= sin-1 (sin2θ) 

= 2θ 

= 2 sin-1

= RHS 

∴ sin-1 (2x - √ (1 – x2)) = 2 sin-1 x



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