A particle moves with its position given by x=cos6t and y=sint , where positions are given in feet from the origin and time t is in seconds.

Find the speed of the particle.

I took the derivative of each equation and then plugged it into the formula velocity=sqrt((dx/dt)^2+(dy/dt)^2).

I got ((-6sin6t)^2+cost^2)^(1/2)ft/s for the answer, but that is incorrect.

Am I going about this the wrong way?