Which one of the following functions is one-one?

Options

A. `f(x)=sinx,x in [-pi,pi]`
B. `f(x)=sinx,x in[-(3pi)/(2),-(pi)/(4)]`
C. `f(x)=cosx,x in[-(pi)/(2),(pi)/(2)]`
D. `f(x)=cosx,x in[pi,(3pi)/(2)]`

Answer

D

Explanation

In the given options (a), (b) and ( c ) the curves are decreasing and increasing in the given intervals, so it is not one-one function. But in option (d), the curve is only increasing in the given intervals, so it is one-one function.