Please Help me! In the figure below, ΔABC is an equilateral triangle. Which is the measure of arc BAC?
60 degrees
120 degrees
240 degrees
270 degrees
http://assets.openstudy.com/updates/attachments/4f79d386e4b0ddcbb89ef0e6-jayjenk-1333384190980-u8testq3.gif

Question

Please Help me! In the figure below, ΔABC is an equilateral triangle. Which is the measure of arc BAC?
                60 degrees
		120 degrees
		240 degrees
		270 degrees
http://assets.openstudy.com/updates/attachments/4f79d386e4b0ddcbb89ef0e6-jayjenk-1333384190980-u8testq3.gif

anonymous · Answer

is it 60 degree?

directrix · Answer

>>is it 60 degree?  No.

The triangle is equilateral and all sides are congruent. Because the triangle is inscribed in the circle, the sides of the triangle are chords of the circle.  In a circle, congruent chords have congruent arcs. So, each arc of these three chords is 360/3 = 120.

Measure of arc BAC = m of arc AB + m of arc AC = 120 + 120 = 240 degrees. --> Ans.