Evaluate each of the following:
As cos(–θ) is cos(θ )
∴ (cos
) = (cos
)
Now,
cos
∴ The question becomes cos–1(
)
Let cos–1
=y
⇒ cos y = 
= cos
The range of principal value of cos–1 is [0,π] and cos 
Therefore, the value of cos–1(cos
) is
.
2
Evaluate each of the following:
As cos(–θ) is cos(θ )
∴ (cos) = (cos)
Now,
cos
∴ The question becomes cos–1()
Let cos–1 =y
⇒ cos y =
= cos
The range of principal value of cos–1 is [0,π] and cos
Therefore, the value of cos–1(cos) is.