Answer:
x = Æ›/4, 3Æ›/4, 5Æ›/4
Step-by-step explanation:
The equation for the transverse wave displacement of a string is given as:
y(x,t) = Acos(kx)sin(wt) = A/2 ( sin(kx + wt) - sin(kx -wt))----------(1)
Since we are aware of the product rule:
cosAsinB = 1/2( sin(A+B) - sin(A - B))
Att = 0, y(x,0) = A/2 (sin(kx - sinkx) = 0
(c) The angular frequency w= 2Ï€/T
Substituting the angular frequency in equation (1) we get
y(x,T/4) = Acos(kx)sin ((2Ï€/T)(T/4))
      = Acos(kx)sin(π/2)
      =Acos(kx)
(d) The first three non-zero nodal points will be:
for y = 0; coskx = 0
kx = π/2, 3π/2, 5π/2
NOW,
k = 2Ï€/ Æ›
(2π/ ƛ)x = π/2, 3π/2, 5π/2
x = ( π/2, 3π/2, 5π,2)*ƛ/2π
x = Æ›/4, 3Æ›/4, 5Æ›/4