Let (x) be the angle of inclination at a point on the graph y = f (x) (see Exercise 69)
Chapter 13, Problem 71(choose chapter or problem)
Let (x) be the angle of inclination at a point on the graph y = f (x) (see Exercise 69). (a) Use the relation f (x) = tan to prove that d dx = f (x) (1 + f (x)2) . (b) Use the arc length integral to show that ds dx = 1 + f (x)2. (c) Now give a proof of Eq. (5) using Eq. (13).
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