Question 5: Find the principal value of cos¯¹ (-1/2)
Class 12 - Math - Inverse Trigonometric Functions
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Let cos-1
(-
1
/2
) = y, then cos y = -
1
/2
= -cos
π
/3
= cos (π- π/3 ) = cos ( 2π /3 )
We know that the range of the principal value branch of cos−¹x is [0, π] and
cos ( 2π /3 ) = - 1 /2
Therefore, the principal value of
cos-1 (- 1 /2 ) is 2π/3
= cos (π- π/3 ) = cos ( 2π /3 )
We know that the range of the principal value branch of cos−¹x is [0, π] and
cos ( 2π /3 ) = - 1 /2
Therefore, the principal value of
cos-1 (- 1 /2 ) is 2π/3
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