1)
http://web2.0calc.com/questions/an-extreme-skier-starting-from-rest-coasts-down-a-mountain-that-makes-an-angle-of-30-9-with-the-horizontal-the-coefficient-of-kinetic-f
2)
http://web2.0calc.com/questions/covariance-of-two-samples
3)
http://web2.0calc.com/questions/how-do-you-find-a-total-mass-using-spherical-shells-for-example-the-total-mass-of-a-spherical-galaxy-with-a-mass-density-at-a-distance-s
4)
http://web2.0calc.com/questions/what-s-the-difference-between-linear-approximation-and-newton-s-method-both-are-similar-in-a-way
+118724 
