Question 378531
Draw the altitude from the top vertex to the base of the triangle.  Then two congruent right triangles will form, one angle being 31 degrees (half of 62 degrees), and opposite it a side measuring 11 units.  The hypotenuse, which corresponds to the leg of the isosceles triangle, is c .  Hence {{{sin 31 = 11/c}}}.  Then {{{c = 11/sin 31 = 21.3576}}}.