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# Angle Relationships & Similar Triangles

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In this lesson, we will learn about a few geometric properties that allow us to find unknown angle measures. We will start with the concept of vertical angles. Vertical angles will always have equal measures. Next, we will look at a transversal the intersects two parallel lines. Here, 8 angles are formed, with properties such that: alternate interior angles are equal in measure, alternate exterior angles are equal in measure, interior angles on the same side of the transversal add up to 180°, and corresponding angles have equal measure. Next, we will learn about the angle sum property of triangles. This property tells us that the sum of the measures of the angles of a triangle will always be 180°. Lastly, we will learn how to work with similar triangles. Similar triangles are triangles that have the same shape. Corresponding angles will be the same and corresponding sides will be proportional. We will tackle problems with similar triangles that involve finding the missing angle or finding the missing length of a given side.

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