sec 4.7: Problem 3 Solve the wave equation with fixed endpoints and the given initial displacement and velocity. Utt = 4uxx, 0 < x < 7, t> 0 t>0 u(0,t)=0, u(7,t) = 0, u(x, 0) ut(x, 0) = = (0, 0 < x < 1/1 ½ < x < 7 [8, 금 5x(7x), 0 < x < 7 We solve the PDE using the series solution u(x,t) = sin (2) ( 7 2nπ 2nπ -bn sin t + cn cos 2nπ 7 7 ·t)). n=1 The coefficients b and c are Fourier coefficients we have computed many times: bn dx Cn = dx help (formulas) help (numbers)

13.2.21 Question Help At time t = 0, a particle is located at the point (4,9,7). It travels in a straight line to the point (6,1,1), has speed 7 at (4,9,7) and constant acceleration 21 - 8j – 6k. Find an equation for the position vector r(t) of the particle at time t. The equation for the position vector r(t) of the particle at timet is r(t) = ( Di+ ( Dij+ () k. (Type exact answers, using radicals as needed.) Enter your answer in the edit fields and then click Check Answer. Clear All Check Answer All parts showing Terms of Use Privacy Policy Permissions Contact Us Copyright 2020 Pearson Education InC. All rights reserved. e to search (27

QUESTION 2 Let r(t)=(-t,2t2,2). Find the speed when t =4.