If A is involutary then|A|=1 or −1
True
We know that for a matrix A to be called as involutery A2 should be equal to I
A2=I
So |A∧2|=|I||A|2=1(as determinant of identity matrix is 1).Also |A|2=|A|=|A|2(Refer to the of determinants which says that |AB|=|A||B|).Here A and B are same only)So |A|=1or−1.