The name triangle is used because all triangles have three angles. Previously you have seen that an equilateral triangle has three equal angles and that an isosceles triangle has two equal angles. Here you will investigate an angle relationship between the three angles of a triangle that is true for any triangle.

• On a separate piece of paper, use a straightedge to draw a triangle.
• Mark the angles of your triangle.
• Cut out your triangle.
• Cut your triangle into 3 pieces so one of the original angles is on each piece.
• Place the three original angles together to form a single angle.

1. What do you notice about the measure of the angle formed by combining the three original angles?
   
   
2. Do you expect this combined angle measure will be the same for all triangles?