[Solved] Unwanted minus sign in this derivative of a circular curve

[nomadreid]

Homework Statement

Find the derivative dy/dx of the curve (circle) expressed in parametric form: (x,y)=(cos t, sin t).

Relevant Equations

dy/dx of (x(t), y(t))= y'(t)/x'(t)

y'(t)/x'(t) = cos t/-sin t = -cot t.
But as t is the angle, and the derivative is the slope, then isn't the slope supposed to be tan t?

 

[phinds]

 

[nomadreid]

Ah, oops. Thanks, phinds. I was mistakenly thinking of the slope of the line from the origin to the point, but now I see that this was a silly mistake. Problem solved, thread closed.