r A POT 



Also CQ*(m0-a)&mfi-[c<(*mfl-*) + 



cot (mff - a) sin m0 . (tin (Imfl - a) + tin ). 



Ham mat ion v (see Trigonometry, Chap, x 

 we < resolved part*, 



/' . IM . 



- o eos a and - tin a. 



i . with the notation <:' 



tan <i - tan a, A* 



Tit-- former equation shews that t tion of the resatt- 



Ir.n with the straight line which joins the om f 



i>e forces act; ami toe Utter equation 

 mines the magnitude of the resultant 



Suppose three forces P, Q, R to act at a point 0. and 

 to lx be described with O as 



, and :i m, ruttii 



nt the |H.intn A. y: then shall // he 



respo ual to the areas of the triangles 



i follows at once from Art. r. ( . since the area of a 

 - expressed by half the product of two sides into the 

 sine o liulcd ai 



Suppose four forces I\ Q, R, S to act at a 



juililiritnn; !!.. i* described with a 



i.l any radiu- the directions of the force* at 



thr point.-* J. l> respe*- 



. y proportional to the volumes of the pyramids 



ke as the origin of a set of rectangular axes, let jr. y t . : 

 co-ordi nates of A ; x 9 , y t , r f the co-ordinates of B; and 



>':.. '1 



, + Qf 9 + Rjr 9 + &r 4 * 



. + Qy, 



f 4 - 



