Example 3 (i) - Chapter 2 Class 12 Inverse Trigonometric Functions (Term 1)

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Example 3 Show that sin−1 (2x√(1−𝑥2)) = 2 sin-1x Solving L.H.S. sin−1 ( 2x √(1−𝑥2) ) Putting x = sin θ = sin−1 ("2 sin θ " √(𝟏−𝒔𝒊𝒏𝟐" θ" )) = sin−1 ("2 sin θ " √(𝒄𝒐𝒔𝟐" θ" )) = sin−1 (2sin θ cos θ) = sin−1 (sin 2θ) (As 1 – sin2 θ = cos2 θ) (Using sin 2x = 2 sin x cos x) (Using sin 2x = 2 sin x cos x) = 2θ = 2 × sin−1 x = 2 sin−1 x = R.H.S. Since L.H.S. = R. H. S. Hence proved As x = sin θ sin-1 x = θ