Why is area of a surface of revolution integral $2\pi y~ds$? not '$dx$'?
7241
Areas versus volumes of revolution: why does the area require approximation by a cone?
156485
How to evaluate $\int_{0}^{2\pi}e^{\cos \theta}\cos( \sin \theta) d\theta$?
8408
What is $dx$ in integration?
89038
Why does the magnitude of the cross-product of a and b give the area of a parallelogram spanned by a and b?
6892
Why is it not true that $\int_0^{\pi} \sin(x)\; dx = 0$?
96023
Prove: $\int_\gamma \bar z \, dz=2i\operatorname{Area}(G)$
35589
Exact area using limits and Riemann sum
29304
Surface integral of a scalar over a unit cube.
37407
Area of intersection of two Annulus
122395
Integrating $\sec\theta\tan^2\theta d\,\theta$
5679
Why is $2\pi i \neq 0?$
127711
Evaluating $\int_{0}^{1}\int_{0}^{1}\sqrt{x^{2}+y^{2}}dxdy$ using polar coordinates.
79561
Transform to polar the following integral $\int_0^6\int_0^y x \, dx \, dy$
124401
How to evaluate $\int_0^{2\pi}\frac{1}{(1+a\cos {\theta})^2}\,d\theta$ without contour integration?
81679
Why is $f(4)$ the area under $f'(x)$ specifically from $0$ to $4$ and not for ex from $1$ to $4$ or $2$ to $4$?
23397
Why it's true? $\arcsin(x) +\arccos(x) = \frac{\pi}{2}$
101524
Finding the volume enclosed by two surfaces of revolution