Recent content by maupassant

Homework Statement Find the surface area of the cone with the following equations: x= u sin(a)cos(v) , y= u sin(a)sin(v), z=u cos(a) where 0<=u <=b , 0<=v<=2(pi), a is constant! The Attempt at a Solution Trying to solve this I first calculate the absolute value of the cross product of r'(u)...

Thank you very much for your help guys!

Homework Statement Let f(x) = x sgn(sin(1/x)) if x != 0 f(x) = 0 if x = 0 on the interval I=[-1,1] Now I 'm asked to show that f(x) is not piecewise continuous on I and later, I must show that f is integrable on I. The Attempt at a Solution I am completely lost here and...

Thanks a lot! I finally got it (at least I hope so ;-) !

Homework Statement Calculate §§ A.n dS if A= 2y(x^2)i-(y^2)j + 4xzk over the region in the first octant bounded by (y^2)+(z^2) = 9 and x = 2 Homework Equations The Attempt at a Solution Let n = (yj + zk) / 3 then A.n = [-(y^3) +4xz^3] / 3...

Thank you for the quick reply but the thing that bothers me is how one reaches inequality 3xi-1<=xi²+xi-1xi<=3xi And why did the author multiply the first and the third factor by 3? I cannot give any reason to do so unless perhaps you work from the result (=(1/3)(b³-a³)) backwards? So...

Hmm should 've used subscripts instead of superscripts... Apologies!

Homework Statement I should have to prove that \int^{b}_____________{a} x² dx = (1/3)(b³-a³) The Attempt at a Solution I know that f is continuous on [a,b] and that there exists a unique number I so that L_{f}(P)\leq I \leq U_{f}(P) . So the first thing to do is to find the...

Thanks for the answer!

Hi everybody, Suppose one wants to prove that lim (3x²-x) = 10 as x approaches 2. Taking the definition of a limit we should have: "If 0 < |x-2| < d then it follows that |f(x) - 10| < e" Proving this statement, we can say |f(x)-10| < e iff |3x²-x-10| <e iff...