Geometry Study Power Point Welcome Elementary School 2014

Lines and Angles 4GA.1 Draw points, lines, line segments, rays, angles (right, acute, obtuse), and perpendicular and parallel lines. Identify these in two-dimensional figures.

Points and Line Segments When you connect two points using a straightedge, you create a line segment A B points

Points, Endpoints and Line Segments B line segment letters are often used to name a line segment ONE name for this line segment is “line segment AB” A short way to write “line segment AB” is AB Another name for this line segment is “line segment BA”

Lines point point A B lines extending line segment AB in both directions and drawing an arrow at each end makes a LINE This line is called “line AB” or “line BA” A short way to write the name of this lines is AB or BA

Short way to write the name is CD Ray endpoint point C D rays line segment that goes on without end in only ONE direction Point C is the ENDPOINT of the ray CD The letter that names the ENDPOINT is ALWAYS written first. Short way to write the name is CD

What is an angle? A angle is two rays or line segments that share a common endpoint, called the vertex. D O G

Naming Angles How to name angles: A B C vertex A B C How to name angles: The vertex is one way to name an angle. The angle here could be named angle B because B is the vertex of the angle. Remember that the middle letter in the name of the angle is always the vertex. You should name this angle CBA or ABC.

Important ideas to remember about angles Angles can be formed by two rays or two line segments that share a common endpoint. The common endpoint is called the vertex. The vertex is always named in the middle of an angle. When you draw an angle, make sure you use a half circle to show the viewer where to look This shouts, look here!

2d Shapes 4GA.2 Classify two-dimensional figures based on the presence or absence of parallel or perpendicular lines, or the presence or absence of angles of a specified size. Recognize right triangles as a category, and identify right triangles.

Quadrilaterals What is a four-sided shape called? quadrangle or quadrilateral Literally means “4” angles or “4” sides QUAD always means four

A triangle is a three-sided shape. Triangles A triangle is a three-sided shape.

Scalene - each side is a different length Isosceles - two sides are the same length Equilateral - all sides are the same length Right Triangle - one of its angles is a right angle (90º) Obtuse Triangle - one of its angles is bigger than 90º Acute Triangle - all of its angles are smaller than 90º

Symmetry 4GA.3 Recognize a line of symmetry for a two-dimensional figure as a line across the figure such that the figure can be folded along the line into matching parts. Identify line-symmetric figures and draw lines of symmetry.

Symmetry: A figure has a line of symmetry when it can be folded along a line so that its two halves match each other exactly.

These letters have a line of symmetry drawn.

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