Calculus
Lesson
36
Arc
Length and Surface Area
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Recall from Pythagorean theorem (or distance formula):
Length of a line:
Taking this to the limit of differentials:
So arc length is typically found by: 
Examples: 
Surface Area: the strip is not a rectangle of differential width, but rather
is a trapezoid, so we don't use dx, but rather ds!
So length is like a thin sliver of a cylinder, with radius p, so length is 2pp.
The differential width is ds.
Examples: 
about
both x and y (for y, use g(y)).