Consider a vector function v : [ a , b ] → V3 , ...i.e. v ( t ) ∊ V3 , t ∊ [ a , b ]. ...Let
vn ...= ...n – 1 ∑ v ( tr ) δnt r = 0
where ...δnt = ( b – a ) ⁄ n , ...and ...tr = a + r δnt. ...Now ...δnt → 0 as n → ∞. define the definite integral of v over [ a , b ] as
...:= ...⌠ b │ v (t) dt ⌡ a limit vn n → ∞
if v is expressed in terms of its coordinate functions:
v (t) ...= ...i vx (t) + j vy (t) + k vz (t)
then
...:= ...i ⌠ b │ v (t) dt ⌡ a
+ ...j ⌠ b │ vx (t) dt ⌡ a
+ ...k ⌠ b │ vy (t) dt ⌡ a ⌠ b │ vz (t) dt ⌡ a