Chain Rule

Chain rule for derivative.
derivative of 1/(z^2+1), chain rule.
derivative of cos(a^3+x^3), chain rule.
derivative of x*e^(-kx), product rule and chain rule.
derivative of ((x^2+1)/(x^2-1))^3.
derivative of sqrt(1+2e^(3x)).
derivative of 5^(-1/x), chain rule.
derivative of r/sqrt(r^2+1).
sect 3.4 #31, derivative of e^(t*sin(2t)).
Sect 3.4 #47, derivative of cot^2(sin(θ)).
derivative of sqrt(5x+1), use the chen lu.
derivative of 4^(c/x), use the chen lu.
derivative of (2x-3)^4*(x^2+x+1)^5, use the chen lu.
derivative of sqrt(x/(x+1)), use the chen lu.
first and second derivative of cos(sin(3x)), use the chen lu.
sect 3.4 #49.