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Find the unknown angle measures
Options: 30°, 51.5°, 60°, 141.5°

51.5 degree

Step-by-step explanation: Since DEF is an isosceles triangle, angle D and F needs to be equal. So substract 77 from 180 and divide by 2.

Step-by-step explanation:

let angle D and angle F be x

x+x+77=180 degree(being sum of the interior angle of a triangle)

2x=180-77

x=103/2

x=51.2 degree

both angle D and F are 51.2 degree because the base angles of an isosceles triangle are equal.

both equations and proportions are better.