: ;i.\ - 



M. M. 



no.is.ft 



// /; 



//. 



no.** 



hut / > l Jf l af,P,-J(Af l y > l 4-Af,/ > a )-.lf l .V,=i(y l -f-yi)(r l - 

 i / ' i / i / / * \fi^ _i_ i//' t \t \f . i / j - \ /" j _. i 



/ i/ i/ / .^JCJf^-f-JfjP^-lfilfj-J^-fy,) 



I-2-: 



-(yi-i-yj)^-- 



- 



This may also be writtm in tho form 



So also if A| repreaen .irea of the triangle in the 



second figure, ili.-n 



AJ-PI^^.A /'// /', 



- 'i > 

 -O, : being negjit 



In UM determinant notation thto may be t ThU to derired by 



I another method in Ex. 41, 



P-" 8 - 



t. ri. 1 1 



jft> 1 

 iHil|i 



