1) To bisect is to equally divide an angle or a line segment, into two equal parts.The bisector of AC divides the line segment AC in its midpoint, so AC≅CB, therefore AC=CB. In addition to this, this is equivalent to say that CB is = 1/2AB.
Finally, this is also true that AC+CB=AB.
2) Clearly AC is not equal to 2AB since AC=CB is = 1/2AB then it is false.