First slide
Functions (XII)
Question

The domain of f(x)=cos(sinx)  is

Moderate
Solution

f(x)=cos(sinx) is defined if cos(sinx)0----(1)

 As we know, 1sinx1 for all xR . So, cosθ0

 (Here, θ=sinx lies in the first and fourth quadrants) 

 i.e., cos(sinx)0 for all x

 i.e., xR

 Thus, the domain of f(x) is R . 

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