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# math

find the area enclosed betwen cycloid X= a(t-sin(t))? How can i solve this problem ? send me the steps

Note by Er Kundan Sharma
3 years, 10 months ago

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If you're going to parametrize the cycloid at least give us both $$x,y$$: $x=a(t-\sin t)\\ y=a(1-\cos t)$

You want to determine the area from $$t=0$$ to $$t=2\pi$$ (i.e. one whole arch), so we write: $A=\int_{t=0}^{t=2\pi}y\,\mathrm{d}x$

Recognize that $$y=a(1-\cos t)$$ and $$\mathrm{d}x=a(1-\cos t)\,\mathrm{d}t$$, so our integral is: $A=\int_0^{2\pi}a^2(1-\cos t)^2\,\mathrm{d}t$

Can you finish this off? · 3 years, 10 months ago

@O B \begin{align*}A&=a^2\int_0^{2\pi}(1-2\cos t+\cos^2 t)\,\mathrm{d}t\\&=a^2\int_0^{2\pi}\left[1-2\cos t+\frac12+\frac12\cos 2t\right]\,\mathrm{d}t\\&=a^2\left[t-2\sin t+\frac12t+\frac14\sin 2t\right]_0^{2\pi}\\&=a^2\left[2\pi+\pi\right]\\&=3\pi a^2\end{align*} · 3 years, 10 months ago