solution

>	plot(sin(x)+sin(x)^2,x=-Pi..2*Pi,y=-1/4..2,tickmarks=[[-Pi="-p",2*Pi="2p"],[-1/4,2]],axesfont=[SYMBOL,15],labels=["",""]);

>	minimize(sin(x)+sin(x)^2,x=-Pi..2*Pi);

>	maximize(sin(x)+sin(x)^2,x=-Pi..2*Pi);