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Show that cos-1 32+2sin-132=5π6.

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Question

Show that `cos^-1  sqrt3/2 + 2 sin^-1  sqrt3/2 = (5pi)/6`.

Sum
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Solution

LHS = `cos^-1  sqrt3/2 + 2 sin^-1  sqrt3/2`

`= cos^-1 (cos  pi/6) + 2sin^-1  (sin  pi/3)  .....[because  cos  pi/6 = sqrt3/2 = sin  pi/3]`

`= pi/6 + 2(pi/3)  .....[because sin^-1 (sin "x") = "x",  cos^-1  (cos  x) = "x"]`

`= pi/6 + (2pi)/3`

`= (5 pi)/6` = RHS.

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Chapter 3: Trigonometric Functions - Miscellaneous exercise 3 [Page 111]

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Balbharati Mathematics and Statistics 1 (Arts and Science) [English] Standard 12 Maharashtra State Board
Chapter 3 Trigonometric Functions
Miscellaneous exercise 3 | Q 33 | Page 111

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