Area of isosceles tiangle

The formula is:

Area = base * height.

With an isosceles triangle, two of the angles are congruent and their opposite sides are congruent. There is one remaining angle (that will be referred to as the top angle) and its opposite side (the base). You will probably have to drop a perpendicular line from the top angle to the base. This will bisect the base into two equal parts. Also, you now have two congruent right triangles.

It depends on what you know with this triangle in order to find its height and/or base. However, use the Pythagorean Theorem and I'm sure you can work it out.