The lengths of all the sides of a triangle will be 21 cm
Explanation:
As we know the perimeter of a triangle = sum of all the sides. Let the three sides of the triangle be a, b, c . When the perpendicular bisect an angle the sides of the triangle become equal. As in the question one side is given 21 the other side also become 21. The perimeter is given 63.
According to the question,
AB=AC=21
AB+AC+BC= 63
21+21+BC=63
42+BC=63
BC=21