7. In triangle ABC, BC is extended to D.
A
ACD =
a+
b
a
a
b
B
b
C
D
ACD is an exterior angle of the triangle.
a and b are interior opposite angles of
ACD.
The exterior angle of a triangle is equal to the sum
of its interior opposite angles.
ZXY = 50° and
8. In triangle XYZ, YZ is extended to P,
Find XZP.
P
XYZ = 34°.
XZP = 50° + 34°.
Z
X
50°
34°
Y
9. In each figure, ACD is a straight line. Find the unknown marked angle.
B
b
A
C
D
a
50°
43°
B
A
110°
D
85
C
Exercise 6, pages 79