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Assignment
1. Prove the Integral Mean Value Theorem: If S is a Jordan measurable set in Rn , f : S → R is continuous, and further if S is compact and path-connected, then there exists a point c→ ∈ S such f(c)→ is equal to the average value of f on S.
2. a) The parametric curve C ⊂ R2 defined by γ(t) = (t3 , t2 ) on [−1, 1] is not a manifold at the point 0 ∈ (−1, 1). However, γ is a C1 function on (−1, 1) and you will recall that our definition of manifold only asked for the function involved to be C1 . Explain why this is not a contradiction.
b) Let U be an open set in Rn , f : U → R a continuous function, and C a curve in U. Prove that the line integral of f on C does not depend on parametrization.
c) Let C be an oriented curve in Rn and F : Rn → Rn a continuous vector field with the property that F(⃗x) = 0 for all ⃗x ∈ C. Prove that ,C F · ds = 0.
3. Let f : Rn → R and F, G : Rn → Rn all be C1 .
a) Show that div(fG) = fdivG + (∇f) · G.
b) Let n = 3. Show that div(F × G) = G · curl(F) − F · curlG.
4. Calculate the area of the region in R2 bounded by the ”hypocycloid” γ(t) = (cos3 (t), sin3 (t)) for t ∈ [0, 2π].