Given: Measure of arc AB = measure of arc BC, Measure of angle x = 60°, measure of angle y = 15°
Find: Measure of arc AC

9514 1404 393

  100°

Step-by-step explanation:

The relevant relation for angle x is ...

  x = (AB +DE)/2

and for angle y, it is ...

  y =(AC -DE)/2

Using the second relation to write an expression for DE, we have ...

  DE = AC -2y

In the first equation, this lets us write ...

  x = (AB +(AC -2y))/2 = (AB +(2AB -2y))/2

  2x = 3AB-2y . . . . . . . . . . . . . . multiply by 2

  (2x +2y)/3 = AB = AC/2 . . . . . add 2y; divide by 3

  AC = (4/3)(x +y) = (4/3)(60° +15°) . . . . multiply by 2, substitute known values

  AC = 100°

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step-by-step explanation: