F2 math deductive geometry

Question

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help me plx.. 20points!~~

Answer 1

最愛解答

DFE=a+b(ext ange of triangle)

DFE+c=135(ext angle of triangle)

a+b+c=135

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2010-12-14 20:52:51 補充：

d=CFG(corr. angle ,AG//DE)

CBF+b=180(adj. angles on a st. line)

CBF=180-b

c+180-b=d(ext angle of triangle)

-b-d=-180-c

b+d=180+c

Answer 2

AngleAFD = d (alt. angles, AF//DE)

Hence angleAFC = 180 - d (adj. angles on st. line)

Thus 180 - d + c = b (ext. angle of triangle)

b + d = 180 + c

Answer 3

I only know the upper question.

a+b= └DFE (ext.└ of triangle)

c+└DFE =135 (ext.└ of triangle)

a+b+c=135

I hope it can help u!