Calculate Arc Length of Hypocycloid Function | Homework Help

[DarkSamurai]

Homework Statement

Find the arc length of r(t) = cos(t)^3 i + sin(t)^3 j
from t = 0 to t = 2 * Pi

It's a hypocycloid that's four cusped.

Homework Equations

s = \int\sqrt{x'^2 + y'^2}

The Attempt at a Solution

x = cos(t)^3
y = sin(t)^3

x' = -3cos(t)^2*sin(t)
y' = 3sin(t)^2*cos(t)

\sqrt{x'^2 + y'^2} = 3* \sqrt{cos(t)^4*sin(t)^2 + sin(t)^4*cos(t)^2}

That simplifies to s = \int 3*\sqrt{1}

So the answer is 6*Pi, but for some reason Maple throws out 6.

 

[Dick]

The radical doesn't simplify to 1. Check that again.