Step 1: Recall the formula to find the radius of the circle inscribed to an isosceles triangle.

              FORMULA :  r = \frac{b}{2} \sqrt{\frac{2a - b}{2a + b}}

                  Where the lateral side a, and base b of the isosceles triangle

Step 2: Plug in the values of lateral side and base into the formula

            EXAMPLE: r=\frac{10}{2}\sqrt{\frac{\left(2*12\right)-10}{\left(2*12\right)+10}}

                                 r = 5 \sqrt{\frac{14}{34}}

                                          r = 5 * 0.645

                                            r = 3.2

Step 3: Recall the area formula of the circle

                Area of the circle = \pi r^2

                    Where r - radius of the circle

Step 4: Substitute the radius values in the area of the circle formula

            EXAMPLE: Area = \pi r^2

                                        = \pi (3.2)^2

                                        = \pi (10.56)

                                        = 33.188