sin(701)=sin(720-19)=sin(720)cos(19)-cos(720)sin(19).
sin(720)=sin(0)=0 and cos(720)=cos(0)=1.
sin(701)=-sin(19)=-P.
Sine and cosine are cyclic functions, repeating every 360 degrees. 720=2×360. That's why 720° is equivalent to zero degrees for the trig functions. It's all because there are 360° in a circle. I revolution is 360° and then you get back to the same point. The trig functions are related to circles, hence cyclic.