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5.2 Congruent Triangles Pythagorean Theorem Angle Bisectors Transformations Constructions Objectives: To review and practice concepts involving congruent triangles, the Pythagorean Theorem, angle bisectors, transformations, and constructions.
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Write all 3 triangle congruence properties you learned last year. ■SSS –If 3 sides of 2 different triangles are congruent, the two triangles are congruent. ■SAS –If two sides and the angle between the sides are congruent in different triangles, the two triangles are congruent. ■ASA –If two angles and the side between the two angles are congruent in different triangles, those triangles are congruent.
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Say whether the triangles are congruent, if so, state why. No AAA Side lengths might not be congruent.
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Pythagorean Theorem a 2 + b 2 = c 2 a b c leg hypotenuse Used to find the missing side of a triangle. Can only be used for right triangles.
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Find the length of the missing sides.
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Perpendicular Bisector ■A line that intersects another segment at a right angle and splits that segment into two equal pieces ■Draw a line segment with endpoints ■Put compass needle on one point and draw a half circle. –Compass needs to be over half as long as the segment. ■Repeat the process from the other endpoint. –Make sure you don’t change the distance on your compass. ■Find the points where the arcs intersect. ■Draw a line through those two points. ■This line is the perpendicular bisector. –Label your right angles. –Label each half congruent
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Angle Bisectors ■A ray which cuts an angle into two congruent angles ■Make an angle. ■Put the compass needle on the vertex ■ Make an arc with your compass so that it intersects both sides of the angle. –Length does not matter. ■Move compass needle to one of the intersection points ■Draw an arc somewhere in the middle of the angle ■Repeat process from the other intersection point. –Be sure to keep lengths the same for this part. –These two arcs should intersect in the middle of the angle. ■Draw a ray from the vertex of the angle through the intersection point ■Label the congruent angles.
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Transformations ■ Translation – to move or slide a shape left, right, up, or down. ■ Reflection – Folding the image over a given line. ■ Rotation – Moving an image around a given point.
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Reflections ■ Over the x-axis – y-coordinate changes sign ■ Over the y-axis – x-coordinate changes sign ■ Over the y = x line – find the inverse of the points Rotations ■ Rotation of 180° (around the origin) - Same as reflecting over x-axis and y-axis. Switch signs on both coordinates.
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Translation, reflection or rotation?
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