It is given in the question that, equal sides of isosceles triangle is a

It is also given that, the given triangle is isosceles right-angled triangle

∴ AC =

AC =

AC =

AC = a

We know that,

Perimeter of triangle = Sum of all sides

∴ Perimeter = (AB + BC + AC)

= (a + a + a)

= 2a + a

= a (2 + )

Hence, option (b) is correct