Calculus derivative problem =)

Can anyone help me determine the derivatives of these two? My algebra skills aren't that great:
x=20/squareroot(1+t^2) and y=20t/squareroot(1+t^2)

Thanks for the help!

dx/dt = -½(20)(1 + t²)^(-3/2) (2t) = -20t/(1 + t²)^(3/2)

dy/dx = 20/√(1 + t²) - ½(20t)(1 + t²)^(-3/2)(2t) = [20(1+ t²) - 20t²]/(1 + t²)^(3/2)

= 20/(1 + t²)^(3/2).