Find the slope of the line tangent to the curve y=cos(2x) at the point where x=pi/6

Answer 1

dy/dx = -2sin(2x)
when x = π/6
slope = dy/dx = -2sin (π/3) = -2(√3/2) = -√3

when x = π/6, y = cos(π/3) = 1/2

so you have the point (π/6 , 1/2) and the slope of -√3

Find the equation of the tangent using your favourite method.