Vector Functions - Whitman College

13 Vector eCurvesWe have already seen that a convenient way to describe a line in three dimensions is toprovide a Vector that points to every point on the line as a parametertvaries, likeh1,2,3i+th1, 2,2i=h1 +t,2 2t,3 + that this gives a particularly simple geometric object, there is nothing special aboutthe individual Functions oftthat make up the coordinates of this Vector any Vector witha parameter, likehf(t), g(t), h(t)i, will describe some curve in three dimensions astvariesthrough all possible the curveshcost,sint,0i,hcost,sint, ti, andhcost,sint, , the first two coordinates in all three Functions trace out the points on theunit circle, starting with (1,0) whent= 0 and proceeding counter-clockwise around thecircle astincreases. In the first case, thezcoordinate is always 0, so this describes preciselythe unit circle in thex-yplane. In the second case, thexandycoordinates still describea circle, but now thezcoordinate varies, so that the height of the curve matches the valueoft.

distance gives the average speed. As ∆t approaches zero, this average speed approaches the actual, instantaneous speed of the object at time t. So by performing an “obvious” calculation to get something that looks like the deriva-tive of r(t), we get precisely what we would want from such a derivative: the vector r′(t) points in the ...

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  Speed, Average, Instantaneous, Average speed, Instantaneous speed

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