A triangle is a closed, flat shape made of exactly three straight line segments joined end to end, creating three sides and three vertices (corners). Triangles may differ in size, orientation, or appearance, but turning or stretching a triangle does not change its defining structure; shapes with curved sides, open boundaries, or more than three sides are not triangles.
A triangle is a shape that has:
To identify a triangle, count its sides and corners.
Example:
A
/ \
/ \
B-----C
Step 1: Start at corner and follow the outside of the shape.
Step 2: Count the straight sides: , , and . There are sides.
Step 3: Count the corners: , , and . There are corners.
Step 4: Check that the sides connect all the way around. The shape is closed.
Because the shape has exactly straight sides, corners, and is closed, it is a triangle.
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