Решите 3 срочно!!!!!!!!!

[latex]a)f(x)=4x+sin2x-4\sqrt2sinx\\ f'(x)=4+2cos2x-4\sqrt2cosx=0\\ 2cos^2x-2sin^2x-4\sqrt2cosx+2cos^2x+2sin^2x+2=0\\ 4cos^2x-4\sqrt2cosx+2=0\\ 2x^2-2\sqrt2x+1=0\\ (\sqrt2x-1)^2=0\\ cosx=\sqrt2/2\\ x=\pi/4+2\pi n b) f(x)= x^2/2-cosx\\ f'(x)=x+sinx=x+tgx\\ sinx=tgx\\ sinx=sinx/cosx\\ cosx=1\\ x=2\pi n [/latex]