plot([x^2*sin(x),2*x*cos(x)], x=-Pi..Pi,color=[black,red]);
plot([x^2*sin(x),2*x*sin(x)+x^2*cos(x)], x=-Pi..Pi,color=[black,red]);
plot([sin(x)/(x^2+1),cos(x)/(2*x)], x=-Pi..Pi,y=-5..5, color=[black,red]);
plot([sin(x)/(x^2+1), ((x^2+1)*cos(x)-2*x*sin(x))/((x^2+1)^2)], x=-Pi..Pi, color=[black,red]);