How to create sine curve

[Jim Dodson]

Make a mask with 2 points one at the far left outside of the frame; the other far right outside — make it perfectly staright

RENDER–>STROKE the mask (make sure you set PAINT STYLE OF STROKE to ON TRANPARENT).

Add WAVE WARP — wave type SINE

adjust and animate to taste using WAVE SPEED and PHASE….

[Colin Braley]

You could also do this via expressions and the write on effect…
Try this expression for the brush position of the write on effect:

//begin
amp = 100;//Height of wave in pixels
freq = 2;//Oscillations per sec
beginTime = 0;//in seconds
endTime = 5;//in seconds

y = amp*Math.sin(freq*time*2*Math.PI) + (thisComp.height/2);

x =linear(time, beginTime, endTime, 0, thisComp.width);

[x,y]
//end

~Colin

[Filip Vandueren]

If you don’t need it still and want it to animate like an oscilloscope,
Find yourself some audio of a very deep sine wave or maybe one that is changes tune a little bit and then use the “Render->Audio Waveform” Filter.