Find the coordinates of the stationary points on these curves and determine their nature.

a. y = 4 sin x + 3 cos x for 0 ≤ x ≤ π/2

b. y = 6 cos x/2 + 8 sin x/2 for 0 ≤ x ≤ 2π

c. y = 5 sin (2x + π/2) for – π/6 ≤ x ≤ 5π/6

d. y = e^x/sin x for 0 ≤ x ≤ π

e. y = 2 sin x cos x + 2 cos x for 0 ≤ x ≤ π