Monotonicity, symmetry, or parity analysis of a trigonometric function

The question asks to determine intervals of increase/decrease, axes of symmetry, centers of symmetry, or even/odd properties of a trigonometric function, or to find extremal domains/values related to these properties.

isi-entrance 2013 Q14 4 marks View
In the interval $( - 2 \pi , 0 )$, the function $f ( x ) = \sin \left( \frac { 1 } { x ^ { 3 } } \right)$
(A) never changes sign
(B) changes sign only once
(C) changes sign more than once, but finitely many times
(D) changes sign infinitely many times
isi-entrance 2015 Q9 4 marks View
In the interval $( 0,2 \pi )$, the function $\sin \left( \frac { 1 } { x ^ { 3 } } \right)$
(a) never changes sign
(b) changes sign only once
(c) changes sign more than once, but finitely many times
(d) changes sign infinitely many times.
isi-entrance 2015 Q9 4 marks View
In the interval $( 0,2 \pi )$, the function $\sin \left( \frac { 1 } { x ^ { 3 } } \right)$
(a) never changes sign
(b) changes sign only once
(c) changes sign more than once, but finitely many times
(d) changes sign infinitely many times.