Tangent
Chapter 11 Limit
Limit
http://archives.math.utk.edu/visual.calculus/
limit((sinx)/x)
http://www.ies.co.jp/math/products/calc/applets/LimSinX/LimSinX.html
http://www.math.psu.edu/dna/calculus/sinlim/sinlimplt.gif