 # Properties of Triangles and Circles

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Videos, games, activities and worksheets to help ACT students review properties of triangles and circles.

Triangles--Properties and Classification
This video briefly explains the properties of a triangle. It also explains the classification of triangles based on angles and side length ratios of triangles. The triangle sum theorem is explained and used in a few applications.
Types of Triangles :
Triangles can be classified by their angle measures and side lengths. For triangles only, equiangular and equilateral have the same implications: all sides and angles are congruent. Isosceles triangles have at least two congruent sides and two congruent angles. Right triangles contain an angle whose measure is 90 degrees. All the angles in an acute triangle are less than 90 degrees. Knowing the different types of triangles is important when solving proofs.

Parts of a Circle :
A chord is a line segment whose endpoints are on a circle. A diameter is a chord that passes through the center of a circle. Another one of the parts of a circle is a radius, which is a line segment with one endpoint at the center and one endpoint on the circle. Congruent circles have congruent radii (the plural of radius). Concentric circles have the same center. A central angle has a vertex on the center and endpoints on the circle.

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