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Evaluate the following : If ∫0k12+8x2⋅dx=π16, find k - Mathematics and Statistics

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Question

Evaluate the following : If `int_0^k 1/(2 + 8x^2)*dx = pi/(16)`, find k

Sum

Solution

Let I = `int_0^k 1/(2 + 8x^2)*dx`

= `(1)/(8) int_0^k 1/(x^2 + (1/2)^2)*dx`

= `(1)/(8) xx (1)/((1/2))[tan^-1 (x/((1/2)))]_0^k`

= `(1)/(4)[tan^-1 2x]_0^k`

= `(1)/(4)[tan^-1 2k - tan^-1 0]`

= `(1)/(4) tan^-1 2k`

∴ I = `pi/(16)  "gives" (1)/(4) tan^-1 2k = pi/(16)`

∴ `tan^-1 2k = pi/(4)`

∴ 2k = `tan  pi/(4)` = 1

∴ k = `(1)/(2)`.

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Fundamental Theorem of Integral Calculus
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Chapter 4: Definite Integration - Miscellaneous Exercise 4 [Page 177]

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Balbharati Mathematics and Statistics 2 (Arts and Science) [English] 12 Standard HSC Maharashtra State Board
Chapter 4 Definite Integration
Miscellaneous Exercise 4 | Q 4.2 | Page 177

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