The unknown angle measures are 51.5° and 51.5° respectively.
What is an isosceles triangle?
An isosceles triangle in geometry is a triangle with two equal-length sides.
Given, side DE = side EF
Then, ∠D = ∠F
So, the sum of all angles of the triangle = 180°
or, ∠D + ∠E + ∠F = 180°
or, ∠F + 77° + ∠F = 180°
or, 2∠F = 180° - 77°
or, ∠F = 103/2 = 51.5°
And, ∠D = 51.5°
Hence, the unknown angle measures are 51.5° and 51.5° respectively.
To learn more about an isosceles triangle
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