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八年级数学解答题一般
题目
如图,在ABC\triangle ABC中,AB=ACAB=AC,BAC=56\angle BAC=56^{\circ},ADAD为中线,AD=AEAD=AE,则EDC=______.\angle EDC=\_\_\_\_\_\_^{\circ}.
知识点:等腰三角形的性质章节:第13章 三角形 / 13.1 三角形的概念

答案与解析

答案

B=C=y\angle B=\angle C=yEDC=x\angle EDC=x
BAC=56\because \angle BAC=56^{\circ}AB=ACAB=AC
B=C=12(180BAC)=62\therefore \angle B=\angle C=\frac{1}{2}(180^{\circ}-\angle BAC)=62^{\circ}
EDC+C=x+y=AED\angle EDC+\angle C=x+y=\angle AED
AD=AE\because AD=AE
ADE=AED=x+y\therefore \angle ADE=\angle AED=x+y
ADC=ADE+EDC=2x+y\therefore \angle ADC=\angle ADE+\angle EDC=2x+y
ADC=B+BAD\because \angle ADC=\angle B+\angle BAD
2x+y=y+32\therefore 2x+y=y+32
x=16\therefore x=16
EDC\therefore \angle EDC的度数是1616^{\circ}.
故答案为:1616.

解析

B=C=y\angle B=\angle C=yEDC=x\angle EDC=x
BAC=56\because \angle BAC=56^{\circ}AB=ACAB=AC
B=C=12(180BAC)=62\therefore \angle B=\angle C=\frac{1}{2}(180^{\circ}-\angle BAC)=62^{\circ}
EDC+C=x+y=AED\angle EDC+\angle C=x+y=\angle AED
AD=AE\because AD=AE
ADE=AED=x+y\therefore \angle ADE=\angle AED=x+y
ADC=ADE+EDC=2x+y\therefore \angle ADC=\angle ADE+\angle EDC=2x+y
ADC=B+BAD\because \angle ADC=\angle B+\angle BAD
2x+y=y+32\therefore 2x+y=y+32
x=16\therefore x=16
EDC\therefore \angle EDC的度数是1616^{\circ}.
故答案为:1616.

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