Question

What is the basic formula for finding the area of an isosceles triangle?

Answer 1

With the base and height: `1/2bh`.

With the base and a leg:
The leg and `1/2` of the base form `2` sides of a right triangle. The height, the third side, is equivalent to `sqrt(4l^2-b^2)/2` though the Pythagorean theorem. Thus, the area of an isosceles triangle given a base and a leg is `(bsqrt(4l^2-b^2))/4`.

I could come up with more if you are given angles. Just ask—they can all be figured out through manipulation, but the most important thing to remember is `A=1/2bh` for all triangles.