Hey, In isosceles triangles there r two equal sides . Base angles is usually used for isosceles triangles .... Diagonals are two lines which intersect each other...
For this case we have the following equation: sin (40o) = b / 20 Clearing b we have: 20 * sin (40o) = b Therefore, the length of the AC segment is given by: b = 12.9 Answer: the length of AC is: b = 12.9