finding minimum

Hello Everyone,


I have m=min(a,1/2a)..I want to find the largest of m.

I differentialted 1/2a with respect to a and set it equal to zero. That
is what we do when we want to find maximum or minimum.

the true answer is a=1/sqrt(2)

May be I am doing something wrong?

Can somebody please help me with this problem?

Thank you

.