Graph the Three Functions $y = \frac { - 1 } { \sqrt { 1 + x ^ { 2 } } }$

Essay

Graph the three functions $y = \frac { - 1 } { \sqrt { 1 + x ^ { 2 } } }$ , $y = \frac { 1 } { \sqrt { 1 + x ^ { 2 } } }$ , and $y = \frac { \sin 2 \pi x } { \sqrt { 1 + x ^ { 2 } } }$ on a common screen. Explain how the graphs are related.