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This lesson explores inscribed angles, their measurements, and their relationships with intercepted arcs. Key objectives include finding the measure of an inscribed angle and the angle formed by a tangent and a chord. The Inscribed Angle Theorem states that the measure of an inscribed angle is half that of its intercepted arc. Additional corollaries reveal that angles inscribed in the same arc are congruent, every angle in a semicircle is a right angle, and opposite angles in an inscribed quadrilateral are supplementary. Engage with examples and assignments to solidify your understanding.
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LESSON 11.3 INSCRIBED ANGLES OBJECTIVE: To find the measure of an inscribed angle To find the measure of an angle formed by a tangent and a chord
CR A intercepts what arc? _____ mO = ____ mCR = ____ mA = ____ 60° 60° 30° INTERCEPTED ARC THEOREM 11-9: The measure of an inscribed angle equals the measure of its HALF INTERCEPTED ARC
QP QP A intercepts what arc? _____ B intercepts what arc? _____ mA = ____ mB = ____ 68° 68° Corollary 1: Angles inscribed in the same arc are CONGRUENT
CDE CDE A intercepts what arc? ______ B intercepts what arc? ______ CDE is a ___________ mA = ____ mB = ____ SEMI-CIRCLE 90° 90° Corollary 2: Every angle inscribed in a semicircle is a RIGHT ANGLE
mA = _____ mB = _____ mC = _____ mD = _____ 108° 90° 72° 90° Corollary 3: The opposite angles of a quadrilateral inscribed in a circle are SUPPLEMENTARY
B A D C mA = mBC = mBCD = 120° 120° 60° THEOREM 11-10: The measure of an angle formed by a tangent and a chord is half the measure of its INTERCEPTED ARC
Ex. #1 Find the value of a and b. 60 = ½ a P a 120°= a 60 T Q 30 b = ½ (a + 30) b S b = ½ (120 + 30) R b = ½ (150) An inscribed is ½ the m of its int. arc. b = 75°
Ex. #2 Find m1. m1 is 90°. 40° 70° 1 ’s inscribed in a semicircle = 90°.
Ex. #3 Find m2. 70° 2 and 38° intercept same arc. 2 38° m2 = 38°. Angles that intcpt the same arc are .
Ex. #4 Find the value of mLJK and y. mLJK = ½ JL J Q ½ JL= mQ = 35° 35 y mLJK = 35° L K s formed by tan.& chord = ½ the intcpt arc.
mQJL = 180° mQJ = 180 - mJL mQJ = 180 - 70 mQJ = 110 y = ½mQJ Ex. #4 Find y. J Q 35 y L K y = 55° An inscribed is ½ the m of its int. arc.
ASSIGNMENT: Page 601 #1-3, 5-21 write the theorems for 5-21