Theory:

Let's see the remarkable property that connects three angles of a triangle.
The sum of the measure of three angles of a triangle is 180°.
Example:
Consider a triangle \(ABC\) with interior angles measures \(∠1\), \(∠2\) and \(∠3\).
 
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By the sum of measure of angles of triangle property, \(∠1 + ∠2 + ∠3 = 180°\).
Important!
In a triangle:
  • If the measure of all angles are different, then all sides are different.
  • If the measure of two angles are equal, then two sides are equal.
  • If the measure of three angles are equal, then three sides are equal and each angle measures \(60°\).
  • Sum of three angles of a triangle is \(180°\).