Understand u-substitution, essential examples,
integral of sec(2x)tan(2x), @0:30
integral of sec^2x*tan^2x, @3:57
integral of sin(x)/(1+cos(x)), @8:07
integral of sin(x)/(1+cos^2x), @16:53
integral of x*sqrt(x^2-1), @23:22
integral of x*sqrt(x-1), @27:00