- #1
spinnaker
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Homework Statement
Find the arc length of one of the leaves of the polar curve r= 6 cos 6θ.
Homework Equations
L = ∫sqrt(r^2 + (dr/dθ)^2) dθ
(I use twice that since the length from 0 to π/12 is only half the petal)
The Attempt at a Solution
I seem to get an integral that can't be solved:
L = 2∫sqrt((6 cos 6θ)^2 + (-36 sin 6θ)^2) dθ
= 2∫sqrt(36 cos^2 6θ + 1296 sin^2 6θ) dθ
I simplify the cos^2 and sin^2 to get
L = 2∫sqrt(36 + 1260 sin^6θ) dθ
= 12∫sqrt(1+35 sin^2 6θ) dθ
but that's where I'm stuck. I have no idea how to do that integral. Any help would be sincerely appreciated!