The find the equation of the line, you need to find the slope. This is done by taking the first derivative, using the product rule for this problem.
y' = 6x(-=sin x)+cos x (6) Now plug in x=π
y' = 6π(-=sin π)+cos π (6)
y' = 6π(0)+(-1)(6) = -6
Now, I can plug my m, x and y values into the following equation
y+6π=-6x+6π Subtract 6π from both sides
y = -6x