已知,如图,△ABC中,AB=AC以AB为直径作圆O交边BC于D.交边AC于E

2个回答

  • 连接OE,OD,AD,

    ∵AB为圆O的直径,

    ∴∠ADB=90°,

    又AB=AC,

    ∴AD为∠BAC的平分线,即∠BAD=∠CAD

    又圆心角∠BOD与圆周角∠BAD都对BD弧又圆心角∠EOD与圆周角∠CAD都对DE弧而圆周角∠BAD=∠CAD,所以BD 弧度数等于DE弧度数.连接BE

    ∵AB为圆O的直径,

    ∴∠AEB=90°,利用勾股定理,AE∧2 +BE∧2= AB∧2 =100, EC∧2 +BE∧2= BC∧2=144,两式相减,得EC∧2 - AE∧2 =44, (EC+AE)X(EC-AE)=AC X(EC-AE)= 10 (EC-AE)=44, 得EC-AE=4.4又(EC+AE)=AC= 10,可知AE=2.8