If for an isosceles triangle, the length of each equal side is 'a' unit and third side is 'b' unit; then its area is:

\(\frac{b}{4}\) \(\sqrt {4a^2 - b^2}\) \(\frac{b}{2}\) \(\sqrt {b^2 - 2a^2}\) \(\frac{a}{2}\) \(\sqrt {3a^2 - b^2}\) \(\frac{\sqrt{4b^2 - a^2}}{2b}\)

\(\frac{b}{4}\) \(\sqrt {4a^2 - b^2}\)

Direct formula = \(\frac{b}{4}\) \(\sqrt {4a^2 - b^2}\)