(2cost - cos2t, 2sint - sin2t) 0 <= t <= pi/2

Here's what I have so far:

x'(t)^2 = 4sin^2(t) - 8(sint)(sin2t) + 4sin^2(2t)

y'(t)^2 = 4cos^2(t) - 8(cost)(cos2t) + 4cos^2(2t)

x'(t)^2 + y'(t)^2 = 4 - 8(sint)(sin2t) + 4sin^2(2t) - 8(cost)(cos2t) +

4cos^2(2t)

What do I do next? And/or am I even doing it right?