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California Standards. Preparation for MG3.1 Identify and construct basic elements of geometric figures (e.g., altitudes, midpoints, diagonals, angle bisectors, and perpendicular bisectors; central angles, radii, diameters, and chords of circles) by using a compass and straightedge.
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California Standards Preparation for MG3.1 Identify and construct basic elements of geometric figures (e.g., altitudes, midpoints, diagonals, angle bisectors, and perpendicular bisectors; central angles, radii, diameters, and chords of circles) by using a compass and straightedge.
Points, lines, and planes are the building blocks of geometry. Segments, rays, and angles are defined in terms of these basic figures.
A point names a location. • A Point A
C l B line l, or BC A line is perfectly straight and extends forever in both directions.
A plane is a perfectly flat surface that extends forever in all directions. P E plane P, or plane DEF D F
GH A segment, or line segment, is the part of a line between two points. H G
A ray is a part of a line that starts at one point and extends forever in one direction. J KJ K
KL or JK Additional Example 1: Naming Lines, Planes, Segments, and Rays Use the diagram to name each figure. A. a line Possible answers: Any 2 points on a line can be used.
Plane or plane JKL Additional Example 1: Naming Lines, Planes, Segments, and Rays Use the diagram to name each figure. B. a plane Possible answers: Any 3 points in the plane that form a triangle can name a plane.
JK, KL, LM, JM KJ, KL, JK, LK Additional Example 1: Naming Lines, Planes, Segments, and Rays Use the diagram to name each figure. C. four segments Possible answers: Write the two points in any order. D. four rays Possible answers: Write the endpoint first.
Caution! When naming a ray always write the endpoint first.
AB, BC, CD, AD B A C D CB, CD, DA, DC Check It Out! Example 1 Use the diagram to name each figure. A. four segments Possible answers: Write the two points in any order. B. four rays Possible answers: Write the endpoint first.
B A AB or DC C D Check It Out! Example 1 Use the diagram to name each figure. C. a line Possible answers: Any 2 points on a line can be used.
B A C D Check It Out! Example 1 Use the diagram to name each figure. D. a plane Possible answers: Any 3 points in the plane that form a triangle can name a plane. Plane R or plane ABC
1 360 An angle () is formed by two rays, or sides, with a common endpoint called the vertex. You can name an angle several ways: by its vertex, by its vertex and a point on each ray, or by a number. When three points are used, the middle point must be the vertex. Angles are usually measured in degrees ((°). Since there are 360° in a circle, one degree is of a circle.
Additional Example 2: Classifying Angles Use the diagram to name each figure. A. a right angle TQS B. two acute angles TQP, RQS
Reading Math mTQS is read as “the measure of angle TQS.”
Additional Example 2: Classifying Angles Use the diagram to name each figure. C. two obtuse angles SQP, RQT
Additional Example 2: Classifying Angles Use the diagram to name each figure. D. a pair of complementary angles TQP, RQS mTQP + mRQS = 47° + 43° = 90°
Additional Example 2: Classifying Angles Use the diagram to name each figure. E. two pairs of supplementary angles TQP, RQT mTQP + mRQT = 47° + 133° = 180° mSQP + mSQR = 137° + 43° = 180° SQP, SQR
C B 90° A D 75° 15° E Check It Out! Example 2 Use the diagram to name each figure. A. a right angle BEC
C B 90° A D 75° 15° E Check It Out! Example 2 Use the diagram to name each figure. B. two acute angles AEB, CED C. two obtuse angles BED, AEC
C B 90° A D 75° 15° E Check It Out! Example 2 Use the diagram to name each figure. D. a pair of complementary angles mAEB + mCED = 15° + 75° = 90° AEB, CED
C B 90° A D 75° 15° E Check It Out! Example 2 Use the diagram to name each figure. E. two pairs of supplementary angles mAEB + mBED = 15° + 165° = 180° AEB, BED mCED + mAEC = 75° + 105° = 180° CED, AEC