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1.6 Angles and Their Measures. An angle consists of two different rays that have the same endpoint. The rays are the sides of the angle. The initial point is the vertex of the angle.
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An angle consists of two different rays that have the same endpoint. The rays are the sidesof the angle. The initial point is the vertex of the angle. The angle that has sides AB and AC is denoted by BAC, CAB, A. The point A is the vertex of the angle. C Sides A B Vertex Angle
Name the angles in the figure: SOLUTION: There are three different angles. PQS or SQP SQR or RQS PQR or RQP P S Q Ex.1: Naming Angles R You should not name any of these angles as Q because all three angles have Q as their vertex. The name Q would not distinguish one angle from the others.
B A C Note: • The measure of A is denoted by mA. The measure of an angle can be approximated using a protractor, using units called degrees(°). • For instance, BAC has a measure of 50°, which can be written as mBAC = 50°.
Angles that have the same measure are called congruent angles. more . . .
MEASURES ARE EQUAL mBAC = mDEF ANGLES ARE CONGRUENT BAC DEF Note – Equal & Congruent are not exactly the same!!! “is congruent to” “is equal to”
Classifying Angles • Angles are classified as acute, right, obtuse, and straight, according to their measures. Angles have measures greater than 0° and less than or equal to 180°.
A point is in the interior of an angle if it is between points that lie on each side of the angle. A point is in the exterior of an angle if it is not on the angle or in its interior. Interior/Exterior
If P is in the interior of RST, then mRSP + mPST = mRST R P S T Postulate 6: Angle Addition Postulate