Answer:
Perpendicular bisector theorem
Step-by-step explanation:
The illustration of the theorem is:
If point B is a perpendicular bisector of Line AC and the length of AC is 10cm
Then

Where
--- Perpendicular bisector
So, the equation becomes



Recall: 

Answer:
16.5+13.6+12.4.17.7= 60.2
60.2÷4 =15.05
Answer : 110 degree
To find angle 1 , we apply outside angle theorem Lets name each point Measurement of arc EF=280 degrees
Measurement of arc GH = 60
Angle D = angle 1
Please refer to the theorem attached below

Now we plug in the values

angle 1 = 110
Measurement of angle 1 = 110 degrees
682 divide by 4 = 170.5
is that right no or yes