FORCES ACTING AT A POINT. .'7 



force All may be resolved force* A 



force* / and the fort- 



V. SI-AII. m. 



roes Al> /' arc in equilibrium by the fint 



And we have from the hypothesis M ' AT, 



EI 



/ A" are proportional to the tide* of 

 y are therefore iu equilibrium bjr 

 y act at a |x 



forces A //. net at a point they a: 



equilibri 



straight lines All, HI, < intersections form 



ngle; an -re by A < sides of this triangle 



forces. I re arrive by mechanical 



flowing geometrical rcmilt the *\<\c* of the 



sectiona of All, C are 



\ I. . ! . /', (7 are three |M)ints on t iference of a 



act along AB an roportkmal to 



thec< t lines in magnitude: shew that the rc*ulunt 

 to tangent at B. 



Denote the forcea by ^ and -Q respectively, llesolve 



angles to the tangent at B\ thus we obtain by 



H 



nnd this is zero, since 



CB nnCAB 



ncc the resultant must act along tlic tangent at II. 



