>>549
0≦t≦π/2

dx/dt = -3 sin(t) cos(t)^2 = -(3/2) sin(2t) cos(t)
dy/dt = 3 cos(t) sin(t)^2 = (3/2) sin(2t) sin(t)

(dx/dt)^2 + (dy/dt)^2 = (9/4) sin(2t)^2

∫_{t = 0 to π/2} (√{(dx/dt)^2 + (dy/dt)^2} ) dt = 3/2