g82 



mx-=pdx, ny^ziqdy, Ma;:^3r . /(i +/>'), M^r:rDy . y'(t+/>, 

 sequitur 



P — dxdy . /et -^^') • /(H- /> • S'" 45 ; 



ttbi substituto valore sinus (J), quem praëbet aequatio (Z>), fiet P seQ 



