Elementary Geometry for College Students (6th Edition)

Published by Brooks Cole

Chapter 2 - Section 2.4 - The Angles of a Triangle - Exercises - Page 93: 19

Answer

m$\angle$B=40$^{\circ}$

Work Step by Step

m$\angle$DAE+m$\angle$1+m$\angle$2=180 m$\angle$DAE+70+70=180 m$\angle$DAE=40$^{\circ}$ m$\angle$A=m$\angle$3+m$\angle$DAE+m$\angle$4 m$\angle$A=30+40+30 m$\angle$A=100$^{\circ}$ Angles 1 and 5 form a straight line so they are supplementary. m$\angle$1+m$\angle$5=180 70+m$\angle$5=180 m$\angle$5=110 m$\angle$3+m$\angle$5+m$\angle$B=180 30+110+m$\angle$B=180 m$\angle$B=40$^{\circ}$

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