(20點) F.2 Maths Question (Pythagors' Theorem)

答案已上載於
http://img24.imagevenue.com/img.php?image=45078_2000_122_1168lo.JPG

3a) coz AB= AD(GIVEN)
so Triangle ABD is an isos. triangle (by definition)
angle ABD=angleAdb(base angles, isos. triangle )
angle ABD+angleADB+y=180degrees (angle sum of triangle)
2angle ABD+y=180degrees
angleABD=(180degrees-y)/2
coz AD=DC (given)
so triangle ADC is an isos. triangle (by definition)
angleDAC= x(base angles, isos. triangle )
angleABD+y+2angleDAC+x =180degrees (angle sum of triangle)
(180degree-y)/2 +y+2x+x=180degrees
y=180degree -6x

3B) coz CA=CB (given)
so triangle ABC is an isos. triangle(by definition)
angle CAB=angleCBA(base angles, isos. triangle )
2((180degrees -y)/2)+x=180degrees
180degrees-(180degrees-6x)+x=180degrees
7x=180degrees
x=(180/7)degrees