Observe that this function is defined for all real numbers We may rewrite this function as
f(x) = cos –1 (sin x)
= cos
cos
−
−






1
π2
x
= 2
x
π −
Thus
f ′(x) = – 1 (ii)
Let f(x) = tan –1 
sin
1
cos
x
x




+
 Observe that this function is defined for all real
numbers, where cos x ≠ – 1; i