You could use the simpler pappus' theorem which goes like this : when you rotate a 2d shape to generate a solid figure, distance travelled by centroid multiplied by area of the 2d shape is equal to volume of 3d shape generated, in case of triangle :
Let us say centroid is x distance in x-axis...
A textbook I am using gives the basic eqn of motion of shm as follows :
X = Asin(wt + €)
V =Awcos(wt+€)
But other textbooks and online sources are interchanging sin and cos in above equations, so which is the correct one? Or does it depend on the phase constant €?