Math Is Fun Forum

LuisRodg

Real Member

Registered: 2007-10-23

Posts: 322

Length of a parametric equation.

I was solving a problem which was to find the length of a parametric equation. I got it down to the first step in the picture and then got stuck. I checked on the online manual and thats how they put the last part. However, I do not understand how they removed the absolute value inside the integral and the 3a/2 becomes 6a?

Last edited by LuisRodg (2008-01-31 13:56:51)

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: Length of a parametric equation.

They've split the integral into 4 equal parts:

Each of those four integrals is equal in this case, so

(Stuff after the integral signs omitted because I'm being lazy)
The absolute value doesn't technically need to be dropped, but it can be since sin x is always positive in (0,π/2).

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Why did the vector cross the road?
It wanted to be normal.

LuisRodg

Real Member

Registered: 2007-10-23

Posts: 322

Re: Length of a parametric equation.

I see now. Thanks a lot.