Let the three angles of a triangle be ∠a,∠b and ∠c.
We know that the sum of the angles of a triangle is 180o.
∴∠a+∠b+∠c=180o
Also, it is given that all the angles are equal in measure.
∴∠a=∠b=∠c
Substituting this in the above equation we get,
∠a+∠a+∠a=180o
⇒3∠a=180o
⇒∠a=180o3=60o
∴ Measure of each angle is 60^o.$
It is an equilateral triangle.