I'm using past papers to help with revision but found this question really difficult. Hope someone can help

Equation of curve: y=(2x-1)tan2x, x is between 0 and pi/4 (including 0)

The curve has a minimum at the point P. The x-coordinate of P is k.

a) Show that k satisfies the equation

4k-sin4k-2=0

I wasn't sure where to start but tried substituting k into the equation of the graph which hasn't helped :s

Thanks