The value of angle EDF is 51.5°
An isosceles triangle is a type of triangle that has at least two equal sides and two equal corresponding angles.
The sign shown on the triangle shows that angle EDF = angle EFD
The sum of angle in a triangle is 180°
represent angle EDF by x
therefore:
x + x + 77 = 180
2x = 180 - 77
2x = 103
x = 103/2
x = 51.5
Therefore, the value of angle EDF is 51.5°