Step 1: Recall the Isosceles triangles properties

          NOTE: Isosceles triangles have two equal sides and two equal angles.

Step 2: Find out the given angle is equal angle or not

            NOTE: If you find the equal sides then you will easily know the angle type  

Step 3:  Add the equal angles

              NOTE: If you know the angle measurement of one equal angle of an

            isosceles triangle, then you'll know the measurement of the other equal

            angle.

            EXAMPLE: = 40 + 40 = 80

Step 4: Subtract the angle sum by the 180

            180 - 80 = 100

Step 5: Calculate the angles when, the given angle is not on of the equal angles

             Step 1: Subtract the know angle from 180°.

                           EXAMPLE: 180° - 26° = 154°

            Step 2: Divide the difference by 2 to get the measure of each angle.

                           EXAMPLE: 154° ÷ 2 = 77°

                           Each angle measures 77°.