RD Sharma - Mathematics (Volume 1)

Book: RD Sharma - Mathematics (Volume 1)

Chapter: 4. Inverse Trigonometric Functions

Subject: Maths - Class 12th

Q. No. 2 of Exercise 4.7

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2

Evaluate each of the following:

cos–1(cos 12)

cos–1(cos x) = x


Provided x ϵ [0,π] ≈ [0,3.14]


And in our equation x is 4 which does not lie in the above range.


We know cos[2nπ – x] = cos[x]


cos(2nπ – 12) = cos(12)


Here n = 2.


Also 4π–12 belongs in [0,π]


cos–1(cos 12) = 4π–12


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