Hello,

Hence the function will be minimal when the denominator will be maximal, that is to say when cos(1/2 x -45) will be minimal, ie = -1

cos(1/2 x-45)=-1=cos(pi)

-> x/2 -45=pi+2kpi

-> x=2pi+90+4kpi=(4k+2)pi + 90

So you have to find k such as x is positive and the least positive.