@Carl Love 

Many many thanks. I will keep using the same command.

@Carl Love 

Thank you so much. This is a great help.

Could you please tell me what  minx-xr/3..maxx+xr/3, y= miny-yr/3..maxy+yr/3 means in the plotting command, please?

plots:-implicitplot(
   Curves, x= minx-xr/3..maxx+xr/3, y= miny-yr/3..maxy+yr/3,
   thickness= 3, gridrefine= 3

@Carl Love 

Hi and thanks for your response. I'm afraid I was typing too late at night and made some mistakes. The actual question says: Find the area of the region enclosed by y=sqrt(x), x=4 and the x-axis. I do not know what commands to use to do this in maple. I also would like to know the maple command for finding the point of intersection of a vertical line and a curve in maple. Would appreciate your help.