dy/dx = dy/dt dt/dx

Now differentiate x=t sin(t) wrt x to get:

1 = dt/dx sin(t) + t cos(t) dt/dx

so:

dt/dx = 1/[sin(t) +y]

Now differentiate y= t cos(t) wrt t to get:

dy/dt = cos(t) - t sin(t) = cos(t) - x

so dy/dx = [cos(t) - x]/[sin(t) +y]

Now the point ((pi/2),0) corresponds to t=p/2 and plugging this into the

above gives us dy/dx at this point is:

[-pi/2]/[1] =-pi/2

RonL