∵gf=bd,bd=cf,∴gf=cf,∠c=∠fgc；

∵∠FGE=∠DBE,∴ Their complementary angle ∠FGC=∠ABC, then ∠ C = ∠ ABC is an isosceles triangle.

∫≈a = 58 ,∴∠c=( 180-58)÷2 = 6 1 .