I need help with arc lengths!?

Question

1) Find the length of the curve, L from point P to point Q.

y = 1/2 x^2 , P(-4, 8) Q(4, 8)

L=?

*i tried it out based on an example from class and i ended up with integ. 1+ tan theta with the limits 4 & -4..now im lost

2) Use Simpson's Rule with n = 10 to estimate the arc length of the curve to six decimal places. Compare your answer with the value of the integral produced by your calculator.

y = xe^-x

0 ≤ x ≤ 40

Answer 1

1) terrible algebra concepts...you believe that √(a² + b²) = a + b ???L= int over [ arctan(-4) , arctan(4) ] of (sec Θ)^3 dΘ...now you need to do an integration by parts and to know how to integrate the secant function

2){ [40 - 0] / 6}  { y(0) + 4 y(4) + 2 y(8) + 4 y(12) + 2 y(16) + 4 y(20) + 2 y(24) + 4 y(28) + 2 y(32) + 4 y(36) + y(40) }...you do the computations...calculator 1 .00000000003