Known: as shown in the figure, in the isosceles triangle ABC, AC = BC, ∠ ACB = 90 & amp; amp; # 176;, line L passes through point C (points a and B are on the same side of line L) Ad ⊥ L, be ⊥ L and D respectively
Make FC ⊥ L in C
∴FC∥AD∥BE
∴∠DAC=ACF,∠BCF=∠CBE
∠ACF+∠BCF=∠ACB=90°
And ∵ DAC + ACD = 90 °, BCE + CBE = 90 °
∴∠DAC=∠BCE;∠ACD=∠CBE
And ∵ AC = BC
∴△ADC≌CEB
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