∫(0,2) |1-x| dx
=∫(0,1) |1-x| dx+∫(1,2) |1-x| dx
=∫(0,1) (1-x) dx+∫(1,2) (x-1) dx
=(x-x²/2)|(0,1)+(x²/2-x)|(1,2)
=1