f(x)=sinx*cosx 1/2*2sinx*cosx=1/2sin2x
k=f`(xo)
f`=1/2*2*cos2x=c0s2x
c0s2x=-V2/2
2x=+-3pi/4+2pi n
x=+-3pi/8 +pi n, neZ
f(x)=sinx*cosx 1/2*2sinx*cosx=1/2sin2x
k=f`(xo)
f`=1/2*2*cos2x=c0s2x
c0s2x=-V2/2
2x=+-3pi/4+2pi n
x=+-3pi/8 +pi n, neZ