18.IF A = [■(0&-tan α/2@tan α/2&0)] and I is the identity matrix of order 2 show that, I + A = (I -

IF A = [■(0&-tan α/2@tan α/2&0)] and I is the identity matrix of order 2 show that, I + A = (I - A) [■(cosα&-sinα@sinα&cosα)]