Math Help - How can I find the equation of this sine wave (attached)?

Hey guys,
Little bit stuck, I need to find out the equation of this sine wave graph (the boldest line). I know the formula is y= or f(x)= sin(2*pi*f*x) but i may have inputted the wrong stuff, I got y-sin(2*pi*1*1); it just appears as a straight line, I am not so hot on the sine wave equations so dont really know what I done wrong :/

Can someone please help me figure out this equation? This is to do with electronics/physics aswell, the period of this sine wave is 1ms and the voltage (which is y axis) is 1V.

Please find the attached file

Thanks
Dan

PS. DO NOT pay any attention to the "Before break frequency" and "At break frequency", nothing to do with what I am trying to figure out!