Study Guides/Maths/Differentiation of sin inverse x
Study Guide · Maths

Differentiation of sin⁻¹(x)

In Class 12 Calculus, finding the derivative of inverse trigonometric functions is a standard requirement. The function sin⁻¹(x) (also written as arcsin(x)) has a very specific and frequently used derivative formula.

Question (Click to Flip)

Why is the domain restricted to -1 < x < 1?

Answer

The domain is restricted because if x = 1 or x = -1, the denominator √(1 - x²) becomes zero, making the derivative undefined (tending to infinity).

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Key Facts

The derivative of cos⁻¹(x) is exactly the same as sin⁻¹(x), except it has a negative sign: -1 / √(1 - x²).

The Formula

The derivative of sin⁻¹(x) with respect to x is:

d/dx [sin⁻¹(x)] = 1 / √(1 - x²)

(Note: This formula is valid only for -1 < x < 1).

Step-by-Step Derivation

We can prove this using implicit differentiation.

Step 1: Let y = sin⁻¹(x) Step 2: This means, sin(y) = x Step 3: Differentiate both sides with respect to x using the chain rule: d/dx [sin(y)] = d/dx [x] cos(y) · (dy/dx) = 1 Step 4: Rearrange to solve for dy/dx: dy/dx = 1 / cos(y) Step 5: We know from the identity sin²y + cos²y = 1, that cos(y) = √(1 - sin²y). Since sin(y) = x, then cos(y) = √(1 - x²). Step 6: Substitute this back: dy/dx = 1 / √(1 - x²).

Questions and Answers

Why is the domain restricted to -1 < x < 1?+

The domain is restricted because if x = 1 or x = -1, the denominator √(1 - x²) becomes zero, making the derivative undefined (tending to infinity).

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