Geometry: An Interactive Journey to Mastery



Solution
D௘ͽ AJIHGFͼ௘&RPPHQW,WLVFRQYHQWLRQWROLVWWKHQDPHVRIWKHYHUWLFHVLQPDWFKLQJRUGHU௘ͽ
E௘ͽ ‘I.
F௘ͽ DE.
G௘ͽ IH.
H௘ͽ AF.
Example 2
([SODLQZK\WKHWZRWULDQJOHVLQFigure 9.4DUHVLPLODU
DQG¿QGWKHYDOXHVRIx and y.
Solution
%RWKWULDQJOHVSRVVHVVDQDQJOHRIPHDVXUHƒDQGDQDQJOHRIPHDVXUHƒVRE\WKH$$SULQFLSOH
WKH\DUHVLPLODU
7KHVLGHRIOHQJWKͼ௘EHWZHHQDQJOHVƒDQGƒ௘ͽPDWFKHVZLWKWKHVLGHRIOHQJWKVRk 
7KHVLGHRIOHQJWKͼ௘EHWZHHQƒDQGWKHXQODEHOHGDQJOH௘ͽPDWFKHVZLWKVLGHyVRy = 3k 
%HFDXVHWKHUHDUHƒLQDWULDQJOHx ƒ
Example 3
D௘ͽ ([SODLQLQGHWDLOZK\'ABD is similar to 'DEF.
E௘ͽ 6KRZWKDWxy = ab.
ͼ௘6HHFigure 9.5௘ͽ

60°

60°

70°

6 70°

3

9

x

y

Figure 9.4

A

x

B

C

E

y

D F

b a

Figure 9.5