Correct this if anything is wrong. Thanks~

Question 4:
Answer should be (sin^6(2t))/12 +c, not /6

Question 7.b):
Answer should be vmax= 4 pi m/s, not just 4 m/s

Question 13.b):
the integration constant (c) is -root(2), not just root(2)

Question 16.b):
lambda = 5, not 2. They had normal vector <1,-2,2> instead of <1,2,2>
Hence, intersection should be at <-1, -9, 24>

Question 19:
Solutions given are incomplete. After their final equation, substitute x=1 in to get y=2, answering the question.