This is how you might draw your sine wave.
The header files had a getmaxx() and getmaxy() for the screen, but you can plug in the numbers that you want, directly, if you don't have these functions.
I'm curious if you can't put in a getchar() right after that is drawn, and then while the screen is being "held" in place, hold down the Ctrl key and press the PrtScrn (print screen) key.
#define pi 3.14159265
ypos = getmaxy() /2;
crest = getmaxy() /4;
width = getmaxx();
for (i=0; i<width; i++)
swing=crest * sin(10*pi*i/width);
putpixel(i, ypos+swing, RED);
putpixel(i, ypos-swing, BLUE);
Which should put your screen into your system's memory. Then just open up Paint (Start >> Show All Programs >> Accessories >> Paint), and paste the sine wave, right into Paint.
Now save the image as a BMP file, in Paint.
I do this with regular screen's to post up screenshots, so it should work for you, as well.