極度困難的中二數學問題 (10分)

6c) x=40 (alt. ∠s AB//CD)
Let CD meet EF on G
∠CGE=40 (alt.∠s BC//FE)
y=55-40=15
7c)∠ECD=∠EDC=(180-48)/2=66
∠EBC=66 (base ∠s isos. △)
∠BEC=56 (∠ sum of △)
x+56+48+66=180 (∠ sum of△)
x=10

8a) ∠DBA=28 (base ∠s isos.△)
∠BDE=∠BED (base ∠s isos.△)
=28+28=56 (ext ∠s of△)
y=56+28=84 (ext ∠s of △)
b) ∠EBA=(180-42)/2 (base ∠ isos △, ∠ sum of △)
∠EAB=69
∠BEC = 69/2 =34.5 (base∠s isos△, ext. ∠ of △)
x=180-42-34.5-69 =34.5 (corr. ∠ AD//EF)
c)∠BAC=60 (∠s of equil. △)
Let ∠CBD be z
∠CBD=∠DCB=∠CED (base ∠s isos △)
60+60+z+z=180 (∠sum of△)
z=30
x=2z=60 (ext ∠of△)
y=60+60+30 (ext ∠of△)

2009-03-15 21:53:01 補充：
y =150