<span>arccos (cos pi/2)=? </span>cos pi/2=0, arccos (0)=?, we know that cos pi/2=0, so cos^-1 (o)= Pi/2, but cos^-1 (o)=arccos (0), so arccos (cos pi/2)=Pi/2
During the birthday 4/7 of the cake was eaten so it remained 1-4/7=3/7 the next day 1/2 of 3/7 was eaten what remained is 3/7 divide by 1/2 to divide we invert the second fraction (1/2) and multiply 3/7 3/7 x 2/1=6/7
