Find an equation of the tangent line to the graph of the function at the given point.

Find an equation of the tangent line to the graph of the function at the given point.

I was given y= (1/3)arccosx and derived it to y=-1 / 3 (1-x^2)^1/2

I don't know what to do next. Please tell me the steps I need to take. I'm not giving the points because I don't just want an answer, I want to know how to do it. Thanks in advance.

Put in the x value of the point (not given).
That will give the slope of the tangent.
Use the point/slope formula for the equation.