length of astroid parametric

[lone dust]

Hey so I wanted to check if I set this up correctly and see how I should go about starting the integral

[bold bridge]

should be correct already

[proper lantern]

Yeah, seems good. Now, notice the following:
4√(9a^2 cos(θ)^4 sin(θ)^2 + 9a^2 cos(θ)^2 sin(θ)^4) = 12a|cos(θ)sin(θ)|√(cos(θ)^2 + sin(θ)^2) = 6a|sin(2θ)|
The rest is easy.

[lone dust]

thank you sm

[proper lantern]

You're welcome!

[lone dust]

@proper lantern hey, I’m now trying to find the surface area for the same curve when we rotate it around x axis

I’m getting two times what the answer should be when I do it

Would u mind looking at my work