788 Work and Energy 4 Special expression in scalar product(p154) F=Fi+Fj+Fk, and dr=dxi +dyj+dck W=F·cF=(Fax+F如+F) =F+["F4+[F W=∫fdx+∫Fdy+∫Fdz 历=W+W+7&8 Work and Energy , and ˆ ˆ ˆ F F i F j F k = x + y + z  . ˆ ˆ ˆ dr = dxi + dy j + dzk       = + + =  = + + f i f i f i z z z y y y x x x B A x y z B A F dx F dy F dz W F dr (F dx F dy F dz)   4 Special expression in scalar product(p154)    W = F x + F y + F z x d y d z d W =W x +W y +W z